2,000 results on '"Scattering rate"'
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2. Drude's lesser known error of a factor of two and Lorentz's correction.
- Author
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Singh, Navinder
- Subjects
- *
SOLID state physics , *THERMAL conductivity , *BOLTZMANN'S equation , *DRUDE theory , *HEAT capacity - Abstract
As is well known, Paul Drude put forward the very first quantitative theory of electrical conduction in metals in 1900. He could successfully account for the Wiedemann–Franz law which states that the ratio of thermal to electrical conductivity divided by temperature is a constant called the Lorenz number. As it turns out, in Drude's derivation there is a lucky cancellation of two errors. Drude's underestimatation (by an order of 100) of the value of square of the average electron velocity compensated for his overestimatation of the electronic heat capacity (by the same order of 100). This compensation or cancellation of two errors lead to a value of the Lorenz number very close to its experimental value; which is well known. There is another error of a factor of two which Drude made when he calculated two different relaxation times for heat conductivity and electrical conductivity; in this article we highlight how and why this error occurred in Drude's derivation and how it was removed 5 years later (in 1905) by Hendrik Lorentz when he used the Boltzmann equation and a single relaxation time. This article is of pedagogical value and may be useful to undergraduate/graduate students learning solid state physics. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Effect of Proton Irradiation on Thin-Film YBa 2 Cu 3 O 7−δ Superconductor.
- Author
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Fogt, Joseph, Weeda, Hope, Harrison, Trevor, Miles, Nolan, and Cho, Kyuil
- Subjects
- *
HIGH temperature superconductors , *CUPRATES , *THIN films , *COPPER , *SUPERCONDUCTORS , *IRRADIATION - Abstract
We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa 2 Cu 3 O 7 − δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6 × 10 16 p / cm 2 . Upon irradiation, T c was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above T c . This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between T c and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov–Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress T c . [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
4. ON DECAYING PROPERTIES OF NONLINEAR SCHRÖDINGER EQUATIONS.
- Author
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CHENJIE FAN, STAFFILANI, GIGLIOLA, and ZEHUA ZHAO
- Subjects
- *
NONLINEAR Schrodinger equation , *SCHRODINGER equation - Abstract
In this paper we discuss quantitative (pointwise) decay estimates for solutions to the 3D cubic defocusing nonlinear Schrödinger equation with various (deterministic and random) initial data. We show that nonlinear solutions enjoy the same decay rate as the linear ones. The regularity assumption on the initial data is much lower than in previous results (see [C. Fan and Z. Zhao, Discrete Contin. Dyn. Syst., 41 (2021), pp. 3973--3984] and the references therein), and, moreover, we quantify the decay, which is another novelty of this work. Furthermore, we show that the (physical) randomization of the initial data can be used to replace the L¹ -data assumption (see [C. Fan and Z. Zhao, Proc. Amer. Math. Soc., 151 (2023), pp. 2527--2542] for the necessity of the L¹-data assumption). [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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5. A note on decay property of nonlinear Schrodinger equations.
- Author
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Fan, Chenjie and Zhao, Zehua
- Subjects
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NONLINEAR equations , *NONLINEAR Schrodinger equation , *SCHRODINGER equation - Abstract
In this note, we show the existence of a special solution u to defocusing cubic NLS in 3d, which lives in H^{s} for all s>0, but scatters to a linear solution in a very slow way. We prove for this u, for all \epsilon >0, one has \sup _{t>0}t^{\epsilon }\|u(t)-e^{it\Delta }u^{+}\|_{\dot {H}^{1/2}}=\infty. Note that such a slow asymptotic convergence is impossible if one further pose the initial data of u(0) be in L^{1}. We expect that similar construction hold the for other NLS models. It can been seen the slow convergence is caused by the fact that there are delayed backward scattering profile in the initial data, we also illustrate why L^{1} condition of initial data will get rid of this phenomena. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
6. Planckian dissipation and non-Ginzburg-Landau type upper critical field in Bi2201.
- Author
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Zang, Qihao, Zhu, Zhengyan, Xu, Zuyu, Qi, Shichao, Ji, Haoran, Li, Yiwen, Wang, Jian, Luo, Huiqian, Wang, Hua-Bing, and Wen, Hai-Hu
- Abstract
Resistivity and Hall effect measurements have been carried out on a micro-fabricated bridge of Bi2201 single crystal at low temperatures down to 0.4 K under high magnetic fields. When superconductivity is crashed by a high magnetic field, the recovered "normal state" resistivity still shows a linear temperature dependence in the low temperature region. Combining with the effective mass and the charge carrier density, we get a linear scattering rate 1/τ = αk
B T/ħ with 0.77 < α < 1.16, which gives a strong evidence of the Planckian dissipation. Furthermore, our results reveal a new type of temperature dependence of the upper critical field, H c 2 (T) = H ∗ (1 − t) / (t + 0.154) , which is totally different from the expectation of the Ginzburg-Landau theory, and suggests the existence of uncondensed Cooper pairs above Hc2 (T) line. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
7. Near-resonant light scattering by an atom in a state-dependent trap
- Author
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T D Karanikolaou, R J Bettles, and D E Chang
- Subjects
dipole traps ,state dependent trap ,heating ,scattering rate ,elastic scattering ,Science ,Physics ,QC1-999 - Abstract
There are an increasing number of experimental scenarios where near-resonant light is applied to atoms tightly trapped in far off-resonant optical fields, such as for quantum optics applications or for atom imaging. Oftentimes, the electronic ground and excited states involved in the optical transition experience unequal trapping potentials. Here, we systematically analyze the effects of unequal trapping on near-resonant atom–light interactions. In particular, we identify regimes where such trapping can lead to significant excess heating compared to atoms in state-independent potentials, and a reduction of total and elastic scattering cross sections associated with a decreased atom–photon interaction efficiency. Understanding these effects can be valuable for achieving maximum efficiency in quantum optics experiments or atom imaging setups, where efficient atom–light interactions on resonance are desired, but achieving equal trapping is not feasible.
- Published
- 2024
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8. A compact model of the backscattering coefficient and mobility of a graphene FET for SiO2 and h-BN substrates.
- Author
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Upadhyay, Abhishek Kumar, Gupta, Deepika, Mathew, Ribu, and Beohar, Ankur
- Abstract
A field-dependent compact model of the backscattering coefficient and quasi-ballistic mobility of charge carriers in graphene has been developed for two different substrates: silicon dioxide ( SiO 2 ) and hexagonal boron nitride (h-BN). The formulation of the backscattering coefficient is performed using the Landauer and McKelvey flux theory in a quasi-ballistic regime. In graphene, the acoustic phonon, surface optical phonon, and charged impurity scattering affect the transport of the charge carriers. This is carefully considered in our formulation of the backscattering coefficient (R) and quasi-ballistic mobility (μ eff) . We find that the graphene field effect transistor (GFET) with the h-BN substrate has lower backscattering and higher quasi-ballistic mobility. The modeled expressions for backscattering coefficient and quasi-ballistic mobility are substituted in the drain (I DS) equation. The results are in good agreement with experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
9. Thermoelectric Effect in NiAu Alloys : Estimating the Seebeck Coefficient from the Density of States of Nickel Impurities in Gold
- Author
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Nerman, Karl and Nerman, Karl
- Abstract
In thermoelectric materials a temperature gradient results in the generation of an electric field – a phenomenon known as the Seebeck effect – making them applicable for powering wearable electronics or for converting waste heat into electrical energy. Generally, a prerequisite for a large Seebeck coefficient is a strong asymmetry for the electronic density of states around the Fermi level. As such, semiconductors have garnered considerably more interest than metals, due to their intrinsic band gaps. Here we investigate the thermoelectric effect in bimetallic NixAu1-x alloys, where the nickel atoms are added as impurities to gold. The strong Seebeck effect here can be attributed to energy-dependent scattering of conducting Au-s electrons into localized Ni-d states around the Fermi level. The scattering rates due to both Ni impurities and the electron-phonon interaction are estimated as being proportional to the density of states of the Ni-d states, as per Fermi's golden rule. Thus, by using Mott's formula in conjunction with the Nordheim-Gorter relation for the calculation of the total Seebeck coefficient due to multiple independent scattering mechanisms, we completely circumvent the issue of calculating any resistivities. The resulting implementation can be seen to be equivalent to the DOS-1 approximation. Using a tight-binding DFT implementation, the Seebeck coefficient and figure of merit are calculated for a range of Ni concentrations and temperatures, with the maximum effect obtained at an Ni concentration of ~ 44 % and temperature T = 1200 K; yielding S = -113 µV/K and zTmax = 0.68. Our calculations are in excellent agreement with recent experiments at high temperature. As such, our work adds to the notion of NiAu alloys having high potential as thermoelectric materials, while simultaneously lending credibility and explanatory power to the DOS-1 approximation.
- Published
- 2024
10. Probing the origin of abnormally strong electron-phonon interaction in phonon transport of semiconductor C3B monolayer.
- Author
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Cheng, Xue, Zhang, Guangwu, Han, Dan, Ji, Ziqing, Xin, Gongming, Yue, Shengying, and Wang, Xinyu
- Subjects
- *
ELECTRON-phonon interactions , *ELECTRON scattering , *ELECTRONIC band structure , *PHONON scattering , *PHONONS , *SEMICONDUCTORS , *MONOMOLECULAR films - Abstract
[Display omitted] • Strong EPI significantly reduces thermal conductivity in the C 3 B monolayer. • The reduction of κ induced by EPI is closely related to electron DOS. • The electronic band structure of C 3 B exhibits multivalley characteristics. • Unusual phenomenon of large el-ph scattering with low el-ph strength is uncovered. • The B atoms of C 3 B break structural symmetry and induce mass disorder scattering. Recently, the two-dimensional semiconductor C 3 B monolayer has attracted much attention owing to its excellent physical, optical, and electronic properties. In this work, the origin of electron-phonon interaction (EPI) on the thermal properties of C 3 B by n -type and p -type doping is systematically investigated via first-principles calculations to provide fundamental knowledge for the thermal management the C 3 B-based electronic devices. The carrier concentrations for the largest reduction of the lattice thermal conductivity (κ) appear at 4 × 1014 cm−2 for n -type and 9 × 1014 cm−2 for p -type, which is closely related to the electron density of states (DOS). The boron (B) atoms break the structural symmetry and induce mass disorder scattering, which renders C 3 B more prone to the influence of EPI. Moreover, the electronic band structure in the C 3 B monolayer exhibits multivalley characteristics, which leads to an intervalley scattering. It is worth noting that the anisotropy in the C 3 B monolayer can be significantly enhanced by EPI. Additionally, an abnormal phenomenon of strong electron-phonon scattering but low electron-phonon coupling strength is found in C 3 B monolayer, which indicates that large electron-phonon coupling strength is sufficient but not necessary for strong electron-phonon scattering. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
11. Optical Properties of Gold After Intense Short-Pulse Excitations
- Author
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P. D. Ndione, D. O. Gericke, and B. Rethfeld
- Subjects
optical properties ,electrical conductivity ,scattering rate ,highly excited matter ,band occupation ,ultrafast relaxation ,Physics ,QC1-999 - Abstract
Intense ultrashort laser pulses can create highly excited matter with extraordinary properties. Experimental and theoretical investigations of these extreme conditions are very complex and usually intertwined. Here, we report on a theoretical approach for the electron scattering rates and the optical properties in gold at elevated temperatures. Our theory is based on the degree of occupancy of the conduction band as well as inputs from ab initio simulations and experimental data. After the electron system has reached a quasi-equilibrium, the occupancy is fully determined by the electron temperature. Thus, our approach covers the important relaxation stage after fast excitations when the two-temperature model can be applied. Being based on the electronic structure of solids, the model is valid for lattice temperatures up to melting but the electron temperature might exceed this limit by far. Our results agree well with recent experimental data for both the collision frequencies and the conductivity of highly excited gold. Scattering of sp-electrons by d-electrons is found to be the dominant damping mechanism at elevated electron temperatures and depends strongly on the number of conduction electrons, hence, revealing the microscopic origin of the conductivity change after heating. The supportive benchmarks with experiments are very valuable as the underlying scattering rates determine a number of other transport, optical and relaxation properties of laser-excited matter.
- Published
- 2022
- Full Text
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12. High-Precision Surface Scattering Measurement System and Uncertainty Analysis Applied in Laser Protective Materials Diagnostics.
- Author
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Yang, Zhen, Yang, Yanbo, Zhang, Yong, Guo, Xinmin, Lu, Kaichang, and Zhang, Jianlong
- Subjects
SURFACE scattering ,ERROR analysis in mathematics ,SURFACE coatings ,LASERS ,INFRARED lasers ,LUMINOUS flux - Abstract
The current measurement system of surface scattering rate applied in laser protective materials has the defects of low accuracy, discontinuous diagnosis region and narrow infrared measuring waveband. In order to make up for these shortcomings, a high-precision material-surface-scattering-rate measurement system based on a three-hole integrating sphere is proposed, which can realize the high-precision quantitative measurement on any region of coating surface from near-infrared to far-infrared band. Firstly, a new quantitative relationship between the luminous flux received by detector and the surface scattering rate of coating is obtained by modifying the existing integrating sphere scattering model. Secondly, a high-precision scattering characteristic measurement system based on a three-hole integrating sphere is designed and achieved. The influence of the main design parameters of the integrating sphere on the expected measuring accuracy of the system is investigated by using a TracePro simulation. Accordingly, the optimal design parameters of the system are given. Then, the main sources of the relative measurement uncertainty for the scattering rate are investigated experimentally, and four main relative uncertainty factors are evaluated quantitatively. Finally, according to the error propagation theory, the total experimental relative measurement uncertainty of the system is obtained, which is ±2.22% and 26–56% higher than the current measuring accuracy. The new coating-scattering-rate measurement system proposed in this paper can provide an effective experimental detection means for high-precision quantitative measurement and a performance evaluation for laser-protective-coating surface-scattering rate. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
13. Experimental evidence of disorder enhanced electron-phonon scattering in graphene devices.
- Author
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Evangeli, Charalambos, McCann, Edward, Swett, Jacob L., Tewari, Sumit, Bian, Xinya, Thomas, James O., Briggs, G. Andrew D., Kolosov, Oleg V., and Mol, Jan A.
- Subjects
- *
CARRIER density , *PHONON scattering , *IMPULSE (Physics) , *ACOUSTIC phonons , *GRAPHENE , *POLARONS , *OPACITY (Optics) - Abstract
Induced disorder in graphene enables changes in electrical and thermal transport. It has been shown previously that disorder is very important for electron cooling in graphene through disorder-assisted electron-phonon scattering, particularly via the supercollisions process. Here we study electron-momentum relaxation due to electron-phonon scattering while increasing the degree of disorder. With in-situ scanning thermal microscopy we monitor the temperature rise in the constriction region of a bowtie-shaped graphene device while increasing the disorder by means of feedback-controlled voltage ramps at high-current densities. Analysis of the combined thermal and electrical measurements in the low bias regime shows that the relative change of the momentum scattering rate vs temperature, as measured at room temperature, increases with strong local disorder. By excluding other candidate mechanisms for this phenomenon, including a change of the charge carriers density and activation of optical phonons, we conclude that the increase we observe in the temperature-dependent component of the scattering rate is likely due to new acoustic phonon scattering channels that open up as disorder increases. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
14. Analytical Study of Carrier Generation Rate in Graphene Nanoscroll.
- Author
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Amiri, Iraj S. and Mohammadi, Hossein
- Subjects
- *
TRANSPORTATION rates , *GRAPHENE , *NANOSATELLITES - Abstract
Graphene nanoscroll introduced recently is another form of a graphene-based two-dimensional material, which is especially attractive in nanoelectronic applications. As carriers can travel ballistically or semi-ballistically, they can reach high-speed and energy if the channel length is enough. Therefore, they can collide and result in an excessive current called ionisation current. As a result, it is important to study this mechanism carefully. In this paper, we propose an analytical approach to calculate an ionisation coefficient. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
15. High-Precision Surface Scattering Measurement System and Uncertainty Analysis Applied in Laser Protective Materials Diagnostics
- Author
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Zhen Yang, Yanbo Yang, Yong Zhang, Xinmin Guo, Kaichang Lu, and Jianlong Zhang
- Subjects
scattering rate ,three-hole integrating sphere ,high precision ,quantitative measurement ,intelligent protective coating ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The current measurement system of surface scattering rate applied in laser protective materials has the defects of low accuracy, discontinuous diagnosis region and narrow infrared measuring waveband. In order to make up for these shortcomings, a high-precision material-surface-scattering-rate measurement system based on a three-hole integrating sphere is proposed, which can realize the high-precision quantitative measurement on any region of coating surface from near-infrared to far-infrared band. Firstly, a new quantitative relationship between the luminous flux received by detector and the surface scattering rate of coating is obtained by modifying the existing integrating sphere scattering model. Secondly, a high-precision scattering characteristic measurement system based on a three-hole integrating sphere is designed and achieved. The influence of the main design parameters of the integrating sphere on the expected measuring accuracy of the system is investigated by using a TracePro simulation. Accordingly, the optimal design parameters of the system are given. Then, the main sources of the relative measurement uncertainty for the scattering rate are investigated experimentally, and four main relative uncertainty factors are evaluated quantitatively. Finally, according to the error propagation theory, the total experimental relative measurement uncertainty of the system is obtained, which is ±2.22% and 26–56% higher than the current measuring accuracy. The new coating-scattering-rate measurement system proposed in this paper can provide an effective experimental detection means for high-precision quantitative measurement and a performance evaluation for laser-protective-coating surface-scattering rate.
- Published
- 2021
- Full Text
- View/download PDF
16. A comparative study of finite frequency scattering rate from Allen, Mitrović–Fiorucci, Shulga–Dolgov–Maksimov, Sharapov–Carbotte and memory function formalisms.
- Author
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Bhalla, Pankaj and Singh, Navinder
- Subjects
- *
ELECTRON-phonon interactions , *COMPARATIVE studies , *ELECTRON density , *DENSITY of states , *POLARONS , *PHONONS - Abstract
We report a comparative study of scattering rates which are calculated using different formalisms such as [P. B. Allen, Phys. Rev. B 3, 305 (1971); S. V. Shulga, D. V. Dolgov and E. G. Maksimov, Physica C 178, 266 (1991); B. Mitrović and M. A. Fiorucci, Phys. Rev. B 31, 2694 (1985); S. G. Sharapov and J. P. Carbotte, Phys. Rev. B 72, 134506 (2005)] and memory function formalism (MemF) [H. Mori, Prog. Theor. Phys. 33, 423 (1965)]. An advantage of this study is that it sheds light on the physical assumptions used in these formalisms. In this context, we consider a case of electron–phonon interaction and discuss frequency- and temperature-dependent behavior of scattering rates. Further, a comparative study of scattering rate proceeds for distinct phonon density of states (PDOS) and electron density of states (EDOS). From the detailed analysis, we observe that the MemF is the most general one and others are based on restrictive assumptions as discussed in this work. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. The effect of Si impurities on the transport properties and the electron-surface phonon interaction in single layer graphene deposited on polar substrates.
- Author
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Mahdouani, M., Gardelis, S., and Bourguiga, R.
- Subjects
- *
SILICON , *METAL inclusions , *OPTICAL properties of graphene , *PHONON scattering , *SURFACE phonons , *AUGER effect , *HAMILTONIAN systems - Abstract
Abstract We investigated theoretically the effect of introducing Si impurities in a single layer graphene (1LG) that had been deposited on a polar substrate on the transport properties of the graphene layer. We consider in our analysis the scattering effects due to the surface optical (SO) phonons located at the interface of the 1LG with various polar substrates such as S i C , hexagonal B N , S i O 2 a n d H f O 2 . Our results demonstrate a reduction of SO phonon-limited (SOPL) mobility, and SOPL conductivity as well as an increase of the SOPL resistivity and of the scattering rate in the presence of Si impurities in the 1LG. Further, we studied the effect of Si impurities on the electron-surface phonon interaction. For our analysis we used the eigenenergies aquired from the tight-binding Hamiltonian in 1LG. Indeed the presence of the Si impurities induces a decrement in the resonant coupling between the electronic sub-levels and the surface vibration modes in monolayer graphene deposited on polar substrates. Finally, we investigated the effect of Si impurities on the Auger scattering process which affects the carriers relaxation. Our results show an enhancement of the Auger scattering rate in the case of the Si-doped 1LG compared to the undoped 1LG. Highlights • Effect of Si impurities on transport properties in one layer graphene on polar substrates (SiO 2 , HfO 2 , SiC , hexagonal BN). • Study of the effect of the Si impurities on electron-surface phonon interaction in one layer graphene on polar substrates. • Investigation of the effect of Si impurities on optical properties in one layer graphene on polar substrates. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
18. Electron-phonon investigation in stanene.
- Author
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Kanga, N.B.-J., Insad, S., and Drissi, L.B.
- Subjects
- *
ELECTRON-phonon interactions , *HOT carriers , *DENSITY functional theory , *QUANTUM perturbations , *CONDUCTION bands - Abstract
Graphical abstract Highlights • Hot carriers are studied in stanene to adapt this material to specific applications. • Electron-phonon coupling vary strongly along crystallographic directions. • Electron linewidth depends mainly on the out-of-plane optical phonon modes. • Linewidth and hot electrons lifetime are determined. Abstract Collecting carriers before they thermalize is the main goal for carrier's cells. This work presents a study on hot carriers in stanene using density functional and many-body perturbation theories. The present approach is applied to investigate the electron linewidth from electron-phonon interaction at 0 K and 300 K. It is shown that electron-phonon linewidth in stanene displays an important temperature dependence as a function of electron energy. Two different cases are considered in this report, first for electron state initially at the valence band maximum and second at the conduction band minimum. It is found that the electron-phonon interaction is strongly dependent on the electron wave vector. This orientation dependence can be used as a basis for transport phenomena. The electron scattering rate at room temperature, projected on the six phonons modes, reveals that the contribution is overall dominated by out-of-plane transversal optical modes (ZO). Another finding is that stanene's hot carriers thermalize at 250 fs, which is faster than in graphene. This study paves the way to explore hot electrons that are difficult to achieve in experiment. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
19. Four-phonon and normal scattering in 2D hexagonal structures.
- Author
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Sun, Guoqing, Ma, Jinlong, Liu, Chenhan, Xiang, Zheng, Xu, Dongwei, Liu, Te-Huan, and Luo, Xiaobing
- Subjects
- *
ATOMIC mass , *PHONON scattering , *THERMAL conductivity , *PHONONS - Abstract
• Four-phonon scattering is significant in 2D hexagonal structures. • Atomic mass ratio's raise enhances four-phonon scattering and weakens N scattering process. • N scattering process is stronger in three-phonon process. Comprehensive understanding of phonon transport will facilitate the exploration of materials. Four-phonon scattering is find to be important to determine thermal conductivity in many materials, and normal scattering (N process) could lead to some unique phonon transport behaviors, especially in 2D materials. In this work, we studied four-phonon and normal scattering in hexagonal structures, both of which were found to be significant. With the increase of atomic mass ratio, the relative four-phonon scattering is gradually enhanced, whereas N process is weakened. Callaway model and Allen's modified models were used to approximate the thermal conductivity, and we find that the models are applicable in some cases with relative weak N scattering intensity. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
20. Annular fuel for VVER-1000 reactor: Moderation impact on neutronic behavior.
- Author
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Ahmed, Md Tanvir and Shelley, Afroza
- Subjects
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NUCLEAR fuels , *CONTROL elements (Nuclear reactors) , *MIXED oxide fuels (Nuclear engineering) , *FAST reactors , *MODERATION , *TRITIUM , *RESEARCH reactors - Abstract
The impacts of moderation on the neutronic behavior of the VVER-1000 reactor assembly have been investigated by using annular fuel and compared with the conventional one. The study revealed that annular fuel shows a softer neutron spectrum, a better control rod worth and 16% less fissile content compared to the conventional fuel. After 60 MWd/kg burnup, annular fuel contains 6.45% and 255.41% more Pu-239 and Pu-241 respectively than the conventional fuel which can be a valuable source of fissile materials for the MOX fuel. Additionally, annular fuel shows a higher degree of symmetry in power peaking factor (PPF), higher scattering rate, 3.41% less tritium production at the beginning of cycle, and better shutdown margin without significant changes in axial & radial flux. From the neutronics point of view, annular fuel can be a propitious replacement of conventional fuel for the VVER-1000 reactor. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. Carrier Scattering in Solids
- Author
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Bandyopadhyay, Supriyo and Bandyopadhyay, Supriyo
- Published
- 2012
- Full Text
- View/download PDF
22. Opposite atom dependence of isotope engineering of thermal conductivity in bulk and 2D GaN.
- Author
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Sun G, Xiang Z, Ma J, Luo X, and Xu D
- Abstract
Isotope engineering has been shown to be an effective means of regulating thermal conductivity. In this work, we studied the isotope engineering of thermal conductivity in bulk and 2D GaN, and diametrically opposite atom isotope dependence is found. That is, Ga isotope has a large effect (77%) on bulk GaN, while the effect of N isotope on the thermal conductivity is negligible. In 2D GaN, however, N isotope effect (20%) is more significant than that of Ga. Understanding of the different isotope dependence is achieved by deeper insight. Due to the relative magnitude of scattering rate, isotopic scattering influences the thermal conductivity of bulk and 2D GaN in different frequency regions, leading to the opposite atom dependence., (© 2023 IOP Publishing Ltd.)
- Published
- 2023
- Full Text
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23. Electronic Interactions
- Author
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Jacoboni, Carlo and Jacoboni, Carlo
- Published
- 2010
- Full Text
- View/download PDF
24. Electron-phonon scattering and Joule heating in copper at extreme cold temperatures.
- Author
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Lan, Tingyue, Ragab, Tarek, and Basaran, Cemal
- Subjects
- *
ELECTRON scattering , *TEMPERATURE effect , *QUANTUM mechanics , *REACTION mechanisms (Chemistry) , *THERMAL properties , *SUPERCONDUCTORS - Abstract
A quantum mechanical model has been used to calculate the full electron-phonon scattering rates in pure copper at extreme cold temperatures. The proposed model uses Fermi’s Golden rule, specific to each scattering mechanism and wave vector state, providing more accuracy and more details than the widely used empirical third power rule for scattering rates. The empirical third power rule is actually only valid in the low-temperature limit. The results are in good agreement with existing experimental data and theoretical calculations with the assumption that the wave vector of a phonon is much larger than the wave vector of an electron (q ≫ k) and three-dimensional density of states converted to one-dimensional density of states to reduce calculation burden by orders of magnitude. The energy generated by Joule heating is calculated using the proposed model and compared with the experimental data from the literatures. Although the results presented are specific to copper, the method is directly applicable to other metals. In addition, the proposed model can be used to study the thermal properties of copper wires in high temperature superconductor power cable applications. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
25. Relaxation Time of Electron - Polar Optical Phonon Field-Induced Tunnel Scattering.
- Author
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Zalinyan, T.A.
- Subjects
- *
ELECTRIC fields , *ELECTRON energy states , *NUMERICAL analysis - Abstract
Theory of electron-polar optical single phonon field-induced tunnel scattering under the influence of an electric field is considered. It is assumed that the non-degenerate polar semiconductor has a spherical parabolic band structure. In low-field regime, an expression for the scattering time is obtained. Dependence of the scattering time (the scattering rate) on the electron energy is analyzed. The results of corresponding numerical computations for an n-GaAs at 300 K are presented. It is established that there is no fracture on the curve of electron scattering time (scattering rate) dependence on the electron energy. [ABSTRACT FROM AUTHOR]
- Published
- 2018
26. An Alternative Approach to the Extended Drude Model.
- Author
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Gantzler, N. J. and Dordevic, S. V.
- Subjects
- *
DRUDE theory , *PLASMA frequencies , *QUASIPARTICLES , *SUPERCONDUCTORS ,OPTICAL properties of solids - Abstract
The original Drude model, proposed over a hundred years ago, is still used today for the analysis of optical properties of solids. Within this model, both the plasma frequency and quasiparticle scattering rate are constant, which makes the model rather inflexible. In order to circumvent this problem, the so-called extended Drude model was proposed, which allowed for the frequency dependence of both the quasiparticle scattering rate and the effective mass. In this work we will explore an alternative approach to the extended Drude model. Here, one also assumes that the quasiparticle scattering rate is frequency dependent; however, instead of the effective mass, the plasma frequency becomes frequency-dependent. This alternative model is applied to the high Tc superconductor Bi2Sr2CaCu2O8+δ (Bi2212) with Tc = 92 K, and the results are compared and contrasted with the ones obtained from the conventional extended Drude model. The results point to several advantages of this alternative approach to the extended Drude model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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- View/download PDF
27. Decompose the electron and phonon thermal transport of intermetallic compounds NiAl and Ni3Al by first-principles calculations.
- Author
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Tong, Zhen and Bao, Hua
- Subjects
- *
THERMAL conductivity measurement , *ELECTRON-phonon interactions , *PHONON scattering , *PERFORMANCE of nuclear reactors , *AXIOMS - Abstract
In order to develop a better understanding of the thermal conduction of the intermetallic compounds NiAl and Ni 3 Al, detailed electron-phonon scattering was investigated by first-principles calculations. The phonon thermal conductivity of NiAl and Ni 3 Al was calculated by considering phonon-phonon and electron-phonon scatterings. It is found that electron-phonon coupling has a strong effect on the phonon thermal conductivity. At a temperature of 100 K, the electron-phonon coupling will induce 55% and 75% reduction in phonon thermal conductivity of NiAl and Ni 3 Al, respectively. Such an effect decreases with increasing temperature. The electron thermal conductivity was also predicted by considering electron-phonon scattering. We find that though the electrons dominate the thermal transport in NiAl and Ni 3 Al at high temperatures, the phonons have significant contribution to the total thermal conductivity in the sub-room temperature range. Moreover, we find that at room temperature phonons with mean free paths between 1 and 100 nm are the dominant contributors to the thermal conductivity, while the mean free paths of dominant electrons are 1–20 nm. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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28. Carrier Scattering by Optical Phonons, Two-Phonon Processes in Photon Absorption, and Spontaneous Polarization in Wurtzites
- Author
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Dutta, Mitra, Brown, Gail J., Ramadurai, Dinakar, Geerpuram, Dwarakanath, Yang, Jiangyong, Kohanpour, Babak, Chen, Chen, Stroscio, Michael A., Saraniti, M., editor, and Ravaioli, U., editor
- Published
- 2006
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29. Terahertz Optoelectronic Property of Graphene: Substrate-Induced Effects on Plasmonic Characteristics
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I-Tan Lin, Yi-Ping Lai, Kuang-Hsiung Wu, and Jia-Ming Liu
- Subjects
graphene ,plasmon ,coupling ,phonon ,scattering rate ,optical conductivity ,terahertz ,Drude model ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The terahertz plasmon dispersion of a multilayer system consisting of graphene on dielectric and/or plasma thin layers is systematically investigated. We show that graphene plasmons can couple with other quasiparticles such as phonons and plasmons of the substrate; the characteristics of the plasmon dispersion of graphene are dramatically modified by the presence of the coupling effect. The resultant plasmon dispersion of the multilayer system is a strong function of the physical parameters of the spacer and the substrate, signifying the importance of the substrate selection in constructing graphene-based plasmonic devices.
- Published
- 2014
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30. Sb2Te3/graphite nanocomposite: A comprehensive study of thermal conductivity
- Author
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V. A. Kulbachinskii, S. Janaky, Sudip Mukherjee, Gangadhar Das, Ramzy Daou, Chandrabhas Narayana, A. K. Deb, Sylvie Hébert, P. Singha, Samir Kumar Bandyopadhyay, Vladimir G. Kytin, Aritra Banerjee, Subarna Das, Antoine Maignan, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), University of Calcutta, Moscow Institute of Physics and Technology [Moscow] (MIPT), Faculty of Physics [MSU, Moscow], Lomonosov Moscow State University (MSU), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Raiganj University, UGC-DAE Consortium for Scientific Research (UGC-DAE ), Bhabha Atomic Research Centre (BARC), and Government of India, Department of Atomic Energy-Government of India, Department of Atomic Energy
- Subjects
Materials science ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Specific heat measurements ,Condensed Matter::Materials Science ,symbols.namesake ,Thermal conductivity ,Thermoelectric effect ,lcsh:TA401-492 ,Graphite ,ComputingMilieux_MISCELLANEOUS ,Nanocomposite ,Condensed matter physics ,Phonon scattering ,Metals and Alloys ,Thermoelectric systems ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,X-ray powder diffraction ,Scattering rate ,Raman spectroscopy ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,symbols ,Phonons ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology - Abstract
International audience; Thermoelectric performance largely depends on the reduction of lattice thermal conductivity (κL). The study of the thermal conductivity (κ) of a Sb2Te3/graphite nanocomposite system demonstrates ∼40% reduction in κL with graphite incorporation. A plausible explanation of intrinsic low κL observed in Sb2Te3 based system is presented by modeling experimental specific heat (Cp) data. Raman spectroscopy measurement combined to X-Ray diffraction data confirms the presence of graphite as separate phase in the composite sample. It is found that phonon scattering dominates heat transport mechanism in the nanostructured Sb2Te3/graphite composite. Large reduction in κL is accomplished by intensifying scattering rate of phonons via various sources. Graphite introduces effective scattering sources, i.e., defects of different dimensionalities in synthesized nanocomposite sample. Furthermore, graphite mediates phonon-phonon coupling and enhances lattice anharmonicity, which causes an intrinsic scattering of phonons with all frequencies in the Sb2Te3/graphite nanocomposite sample. Dislocation density and phonon anharmonicity of the synthesized samples are estimated from in depth analysis of temperature dependent synchrotron powder diffraction and Raman spectroscopic data. κL value as low as 0.8 W m−1K−1 at 300 K, achieved with graphite dispersion in Sb2Te3 based composite system makes the present comprehensive study an interesting concept to be developed in thermoelectric materials.
- Published
- 2021
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31. The first-principles and BTE investigation of phonon transport in 1T-TiSe2
- Author
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Zhaoliang Wang, Guofu Chen, Dawei Tang, and Xiaoliang Zhang
- Subjects
Materials science ,Condensed matter physics ,Phonon ,Scattering ,Anharmonicity ,General Physics and Astronomy ,02 engineering and technology ,Grüneisen parameter ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,01 natural sciences ,Boltzmann equation ,Thermal conductivity ,Scattering rate ,0103 physical sciences ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology - Abstract
Through the first-principles density functional theory and the phonon Boltzmann transport equation, we investigated the phonon transport characteristics inside 1T-TiSe2. The calculation results of the lattice thermal conductivity (κl) show that the κl of TiSe2 is extremely low (1.28 W (m K)−1, 300 K) and decreases with the shrinkage of the sample size. Moreover, the results also prove the isotropic nature of thermal transport. By decomposing the contribution of the thermal conductivity according to the frequency, the κl of the single-layer TiSe2 is primarily attributed to the acoustic phonons and a small portion of optical phonons, with the frequency range of 0–4.5 THz. The calculation of the scattering rate further illustrates the competition of different scattering modes in this frequency range to verify the change in thermal conductivity of different sample sizes. The high scattering rate and low group velocity lead to the low thermal conductivity of the optical phonon mode in TiSe2. In addition, reducing the size of the system can significantly limit the thermal conductivity by eliminating the contribution of long mean free path phonons. When the characteristic length of the single-layer TiSe2 is about 14.92 nm, κl reduces to half. Our results also show that TiSe2 has an extremely high Gruneisen parameter (about 2.62). Further decomposition of the three-phonon scattering phase space and scattering rate demonstrates that in the range 0–4.5 THz, the absorption process is the main conversion form of phonons. We conclude that, due to the high Gruneisen parameter, the high anharmonicity in TiSe2 leads to the extremely low κl. This study provides κl related to the temperature, frequency, and MFP, and deeply discusses the phonon transport in TiSe2, which has great significance to further adjust the thermal conductivity to develop highly efficient thermoelectric materials and promote the application of devices based on TiSe2.
- Published
- 2021
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32. Electronic properties of Mn-doped graphene
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Ankur Dwivedi, Prafulla K. Jha, Keyur Sangani, Ankur Pandya, and Shibu G. Pillai
- Subjects
010302 applied physics ,Materials science ,Condensed matter physics ,Graphene ,Carrier scattering ,Scattering ,Doping ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,Effective mass (solid-state physics) ,Electrical resistivity and conductivity ,law ,Condensed Matter::Superconductivity ,Scattering rate ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
Carrier scattering rates and transport properties such as electron effective mass and resistivity are calculated for Mn doped armchair graphene (AG) via polar acoustical phonon (piezoelectric) scattering under high electric field and different doping concentrations. It is observed that the electron effective mass reduces with respect to AG on manganese doping. However, in contradiction to this reduction, the electron effective mass increases with the doping concentration. The scattering rate offered by polar acoustical phonons to the electrons is dominant at lower temperatures and significantly reduces with the increase in temperature. The polar acoustical phonon contributed resistivity increases with the rise in electric field at low temperatures.
- Published
- 2021
- Full Text
- View/download PDF
33. 激光环境散射率测量装置的设计.
- Author
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高爱华, 彭东东, and 闰丽荣
- Abstract
In some high precision optical measurement, the scattering particles in the normal atmospheric environment will produce interference on the measurement results. Particularly, if the signal is very weak, the impact will not be ignored, such as the detection of ultra smooth optical surface, high reflecting mirror scattering rate, etc. we need to consider the environmental impact on the measurement results. To solve the problem, an atmospheric scattering rate measuring device is introduced for measuring the ordinary particles in the atmospheric environment on the laser scattering rate. The device can reflect the degree of light scattering measurement environment, and then assess whether the environment can meet the scattering measurement. The device takes a stable power laser as the light source, the light beam passes through the integrating sphere cavity, so the particles in the cavity are scattered, the scattered light is collected by the integrating sphere, and then the scattered light intensity of the integrating sphere is measured by the photoelectric multiplier tube. The signal processing is performed by the correlation detection method which can effectively remove the background noise. In the laboratory environment, the measurement accuracy is up to 0.1 x 10-6, the device error can reach ±2% , and the high precision measurement of scattering rate is achieved. [ABSTRACT FROM AUTHOR]
- Published
- 2017
34. Investigation of the electron-surface phonon interaction effects in graphene on a substrate made of polar materials.
- Author
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Mahdouani, M.
- Subjects
- *
GRAPHENE , *ELECTRON-surface impact , *PHONONS , *SEPARATION (Technology) , *SCATTERING (Physics) , *POLARONS - Abstract
We present a theoretical study of the electron- surface phonon interaction in mono-layer graphene (1LG) on polar substrates such as SiO 2 , HfO 2 , SiC and hexagonal BN . Thus we have used the eigen energies derived from the tight-binding Hamiltonian in mono-layer graphene. Our results indicate that the electron-surface phonon interaction depends on the polar substrate. Such polar substrates allow for the existence of polar optical phonons localized near the graphene-substrate interface which could be an important scattering source for graphene carriers through the long-range Fröhlich coupling. Likewise, we have investigated the effect of various dielectrics on the SO phonon-limited mobility, the SO phonon-limited resistivity, the SO phonon-limited conductivity and the scattering rate in single layer graphene by considering the effects of the SO optical phonon scattering arising from the polar substrates and by varying the temperature, the charge carrier density and the physical separation between graphene and interface of dielectric substrate. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
35. Auger and carrier-surface phonon interaction processes in graphene on a substrate made of polar materials.
- Author
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Mahdouani, M. and Bourguiga, R.
- Subjects
- *
SURFACE phonons , *AUGER effect , *GRAPHENE , *ELECTRON-phonon interactions , *HAMILTONIAN mechanics , *MONOMOLECULAR films - Abstract
We present a theoretical study of two specific dynamical optical properties, namely Auger and surface electron-phonon interaction processes in monolayer graphene on polar substrates such as S i O 2 , H f O 2 , S i C and hexagonal B N . Thus the eigenenergies have been derived from the tight-binding Hamiltonian in monolayer graphene. Our results indicate that both Auger and electron-surface phonon interaction processes depend on the polar substrate. Such polar substrates allow for the presence of polar optical phonons localized near the graphene-substrate interface which could be a significant scattering source for graphene carriers across the long-range Fröhlich coupling. Furthermore, the linear, gapless band structure of graphene provides ideal conditions for Auger processes which are Auger recombination (AR) and impact ionization (IMI). These processes are of fundamental interest because they strongly influence the relaxation dynamics of carriers. Likewise, we have investigated the effect of various dielectrics on both Auger and electron–surface phonon scattering rates in single layer graphene by varying the temperature, the charge carrier density and the physical separation between the interface of the dielectric substrate and graphene. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
36. Analysis of electron transport in AlGaN/GaN superlattice HEMTs for isotopes 14N and 15N.
- Author
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Mazumdar, Kaushik, Ranjan, Rajeev Kumar, Shankar, Ravi, Sharan, Ahna, Priyadarshini, Bindu, Kundu, Mainak, and Ghosal, Aniruddha
- Subjects
- *
SUPERLATTICES , *PHOTONIC band gap structures , *SEMICONDUCTORS , *ELECTRON mobility , *ENERGY-band theory of solids - Abstract
There has been considerable interest in superlattice structures of large band gap semiconductors like AlGaN/GaN based arrangements due to its measured parameter and favorable material properties, such as high electron mobility and very high thermal conductivity. Hence, an understanding of the electron transport in GaN has always been prioritized to improve the GaN semiconductors based devices. Here the transport properties of electron in isotopically mixed Ga 14 N 15 N alloy channels have been studied. Different ratio of isotopes has been considered and their effect on the alloy scattering phenomenon of specimen is studied. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
37. Surface-acoustics phonon scattering in 2D-hole gas of diamond based FET devices
- Author
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Michael A. Stroscio, Sidra Farid, Ramji Singh, A. Glen Birdwell, Mitra Dutta, Tony Ivanov, Giorgio Bonomo, and Mahesh R. Neupane
- Subjects
Materials science ,Condensed matter physics ,Phonon scattering ,Phonon ,Scattering ,Diamond ,02 engineering and technology ,General Chemistry ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Scattering rate ,symbols ,engineering ,Fermi's golden rule ,Relaxation (physics) ,General Materials Science ,Rayleigh wave ,0210 nano-technology - Abstract
We report on the effects of surface-acoustic phonon scattering on the charge transport behavior of diamond based FET devices. Motivated by the promising role of diamond in the realization of high power and high frequency electronic devices, the present work is focused on detailed formulation of relaxation times due to the hole-surface-acoustic phonon scattering, which appears to have been an overlooked scattering mechanism important to diamond-based devices. The matrix element, scattering rates and relaxation times have been calculated by taking into account, for the first time Rayleigh waves near the surface. This is achieved by quantizing the Rayleigh waves and using the corresponding acoustic phonon to calculate the Fermi golden rule based scattering rate of holes in the two-dimensional hole gas. The results show that the scattering of holes with surface acoustic Rayleigh waves reduced relative to scattering from bulk 3D acoustic phonons. Moreover, the mobilities are found to be higher than those based on the theory for 3D acoustic phonons. The results reveal significant insights to diamond based electronics having acoustic phonons Rayleigh waves thus opening new research endeavors.
- Published
- 2020
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- View/download PDF
38. Near-field radiative heat transfer between high-temperature superconductors
- Author
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Raul Esquivel-Sirvent, S. G. Castillo-López, Carlos Villarreal, and Giuseppe Pirruccio
- Subjects
Free electron model ,Physics ,Superconductivity ,Work (thermodynamics) ,Multidisciplinary ,High-temperature superconductivity ,Condensed matter physics ,lcsh:R ,lcsh:Medicine ,Detailed balance ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,law ,Thermal radiation ,Scattering rate ,Condensed Matter::Superconductivity ,0103 physical sciences ,Charge carrier ,lcsh:Q ,010306 general physics ,0210 nano-technology ,lcsh:Science - Abstract
Near-field radiative heat transfer (NFRHT) management can be achieved using high-temperature superconductors. In this work, we present a theoretical study of the radiative heat transfer between two $$\hbox {YBa}_2\hbox {Cu}_3\hbox {O}_{6.95}$$ YBa 2 Cu 3 O 6.95 (YBCO) slabs in three different scenarios: Both slabs either in the normal or superconducting state, and only one of them below the superconductor critical temperature $$T_c$$ T c . The radiative heat transfer is calculated using Rytov’s theory of fluctuating electrodynamics, while a two-fluid model describes the dielectric function of the superconducting materials. Our main result is the significant suppression of the NFRHT when one or both of the slabs are superconducting, which is explained in terms of the detailed balance of the charge carriers density together with the sudden reduction of the free electron scattering rate. A critical and unique feature affecting the radiative heat transfer between high-temperature superconductors is the large damping of the mid-infrared carriers which screens the surface plasmon excitation.
- Published
- 2020
- Full Text
- View/download PDF
39. Analysis of Phonon Modes and Electron–Phonon Interaction in Quantum-Cascade Laser Heterostructures
- Author
-
A. A. Afonenko, An. A. Afonenko, Alexander A. Dubinov, and Dmitrii V. Ushakov
- Subjects
Phonon ,Superlattice ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,law ,Condensed Matter::Superconductivity ,0103 physical sciences ,Energy level ,010302 applied physics ,Physics ,Condensed matter physics ,business.industry ,Heterojunction ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Semiconductor ,Scattering rate ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,business ,Ternary operation ,Quantum cascade laser - Abstract
The phonon modes of quantum-cascade heterostructures based on binary and ternary semiconductor compounds are simulated. The dependences of the frequencies of the structure interface phonon modes on the wave vector in the layer plane and on the phase shift in the superlattice period are calculated. It is found that the range of variation in the quantum energy of phonon modes of the GaAs/Al0.25Ga0.75As structure does not exceed 2 meV. The calculated resulting interband scattering rate in the structure, taking into account the interface and confined modes, barely differs from that calculated in the bulk phonon approximation.
- Published
- 2020
- Full Text
- View/download PDF
40. Linear resistivity and Sachdev-Ye-Kitaev (SYK) spin liquid behavior in a quantum critical metal with spin-1/2 fermions
- Author
-
Nils Wentzell, Antoine Georges, Olivier Parcollet, Eun-Ah Kim, and Peter Cha
- Subjects
Physics ,marginal Fermi liquid ,Multidisciplinary ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed matter physics ,cuprate superconductors ,FOS: Physical sciences ,Planckian metals ,strange metals ,Sachdev-Ye-Kitaev models ,Fermion ,Electron ,Condensed Matter - Strongly Correlated Electrons ,Electrical resistivity and conductivity ,Scattering rate ,Quantum critical point ,Physical Sciences ,Condensed Matter::Strongly Correlated Electrons ,Fermi liquid theory ,Quantum spin liquid ,Quantum - Abstract
Significance In “Planckian metals,” electrons dissipate energy at the fastest possible rate allowed by the fundamental laws of quantum mechanics, resulting in a linear temperature dependence of their electrical resistivity. Although observed for a number of quantum materials, this phenomenon lacks a general theoretical understanding and is often considered as one of the prominent fundamental questions in condensed matter physics. Here, we show that Planckian dissipation and a behavior consistent with the “marginal Fermi liquid” phenomenology emerge in the quantum critical regime separating a Mott insulating spin glass and a Fermi liquid. By establishing this behavior in an explicit model solvable by state-of-the-art computational methods, our theory paves the way toward a deeper understanding of Planckian or “strange” metals., “Strange metals” with resistivity depending linearly on temperature T down to low T have been a long-standing puzzle in condensed matter physics. Here, we consider a lattice model of itinerant spin-1/2 fermions interacting via onsite Hubbard interaction and random infinite-ranged spin–spin interaction. We show that the quantum critical point associated with the melting of the spin-glass phase by charge fluctuations displays non-Fermi liquid behavior, with local spin dynamics identical to that of the Sachdev-Ye-Kitaev family of models. This extends the quantum spin liquid dynamics previously established in the large-M limit of SU(M) symmetric models to models with physical SU(2) spin-1/2 electrons. Remarkably, the quantum critical regime also features a Planckian linear-T resistivity associated with a T-linear scattering rate and a frequency dependence of the electronic self-energy consistent with the marginal Fermi liquid phenomenology.
- Published
- 2020
- Full Text
- View/download PDF
41. Dynamically tunable thermal transport in polycrystalline graphene by strain engineering
- Author
-
Yuqiang Zeng, Zhihong Chen, Chun-Li Lo, Amy Marconnet, and Shengjiao Zhang
- Subjects
Materials science ,business.industry ,Graphene ,Phonon ,02 engineering and technology ,General Chemistry ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Flexible electronics ,0104 chemical sciences ,law.invention ,Strain engineering ,Thermal conductivity ,law ,Scattering rate ,Optoelectronics ,General Materials Science ,Grain boundary ,0210 nano-technology ,business - Abstract
Strain engineering on the thermal conductivity of graphene has attracted significant interest both from the fundamental physics and with applications in mind such as flexible electronics and sensors. But existing computational studies predict inconsistent impacts of strain on thermal transport in graphene, and it is challenging to experimentally quantify. Here, we measure the strain-dependent thermal conductivity of polycrystalline multilayer graphene (MLG) grown by chemical vapor deposition (CVD). The room-temperature thermal conductivity of the MLG film dramatically decreases from 551 ± 28 W/m-K to 395 ± 20 W/m-K with 1% uniaxial strain. The significant decrease (∼28%) of the thermal conductivity is attributed to the increased phonon-grain boundary scattering rate and the reduced probability of specular phonon transmission across the grain boundaries. These findings demonstrate dynamically tunable thermal transport in graphene by strain engineering and emphasize that strain-dependent property characterization is crucial for ensuring the performance and reliability of flexible graphene-based electronics and sensors.
- Published
- 2020
- Full Text
- View/download PDF
42. Flat Bands and Salient Experimental Features Supporting the Fermion Condensation Theory of Strongly Correlated Fermi
- Author
-
E. V. Kirichenko, Vasily R. Shaginyan, Vladimir A. Stephanovich, George Japaridze, M. Ya. Amusia, and Alfred Z. Msezane
- Subjects
Condensed Matter::Quantum Gases ,Quantum phase transition ,Superconductivity ,Physics ,Nuclear and High Energy Physics ,Condensed matter physics ,010308 nuclear & particles physics ,Fermion ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electrical resistivity and conductivity ,Quantum critical point ,Scattering rate ,0103 physical sciences ,Fermi liquid theory ,010306 general physics ,Fermi Gamma-ray Space Telescope - Abstract
The physics of strongly correlated Fermi systems, being the mainstream topic for more than half a century, still remains elusive. Recent advancements in experimental techniques permit to collect important data, which, in turn, allow us to make the conclusive statements about the underlying physics of strongly correlated Fermi systems. Such systems are close to a special quantum critical point represented by topological fermion-condensation quantum phase transition which separates normal Fermi liquid and that with a fermion condensate, forming flat bands. Our review paper considers recent exciting experimental observations of universal scattering rate related to linear temperature dependence of resistivity in a large number of strongly correlated Fermi systems as well as normal metals. We show that the observed scattering rate is explained by the emergence of flat bands, while the so-called Planckian limit occurs accidentally since the normal metals exhibit the same scattering rate behavior. We also analyze recent challenging experimental data on tunneling differential conductivity collected under the application of magnetic field on the twisted graphene and the archetypical heavy fermion metal YbRh $${}_{2}$$ Si $${}_{2}$$ . Also we describe recent empirical observations of scaling properties related to universal linear-temperature resistivity for a large number of strongly correlated high-temperature superconductors. We show that these observations support the fermion condensation theory. Our theoretical results are in good agreement with corps of different and seemingly unrelated experimental facts. They show that the fermion-condensation quantum phase transition is an intrinsic property of strongly correlated Fermi systems and can be viewed as the universal agent explaining their core physics.
- Published
- 2020
- Full Text
- View/download PDF
43. Effects of molecular adsorption on the spin-wave spectrum and magnon relaxation in two-dimensional Cr2Ge2Te6
- Author
-
Min Zhang, Ke Wang, Hai Wang, Yuan Cheng, Gang Zhang, and Kai Ren
- Subjects
Materials science ,Condensed matter physics ,Scattering ,Magnon ,Relaxation (NMR) ,Exchange interaction ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Spin wave ,Molecular vibration ,Scattering rate ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Wave vector ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology - Abstract
In this work, we performed detailed first-principles calculation and theoretical analysis to investigate the effect of molecular adsorption on the spin-wave spectrum and magnon relaxation in a Cr2Ge2Te6 (CGT) monolayer. It is found that NH3, NO, and NO2 adsorption can enhance the exchange constant of CGT, which can result in a blue-shift in the spin-wave spectrum. At 30 K, by means of a thorough investigation of many possible lattice configurations excited by thermal fluctuation, we identify the magnon scattering rate from the intrinsic lattice vibrational modes, and find that the relaxation of optical and acoustic magnons exhibits a completely different wave vector dependence. Moreover, although the adsorption of NO2 and NH3 molecules has a negligible influence on the magnon–phonon interaction, the adsorption of NO molecules results in a significant increase in magnon scattering strength. In the long-wavelength limit, the interlayer vibrational modes induced by NO adsorption increase the magnon–phonon scattering strength by ∼12.7%. The remarkable interlayer magnon–phonon interaction is ascribed to the strong CGT–NO coupling and large molecular vibration amplitude. Considering the importance of magnon relaxation time in the application of spin devices, we suggest that both the impacts on the exchange interaction and scattering rate must be considered when manipulating two-dimensional magnets by surface functionalization.
- Published
- 2020
- Full Text
- View/download PDF
44. Universal Bottleneck for Thermal Relaxation in Disordered Metallic Films
- Author
-
N.A. Titova, V. S. Khrapai, E. M. Baeva, S. U. Piatrusha, and A. I. Kardakova
- Subjects
Superconductivity ,Physics ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics and Astronomy (miscellaneous) ,Phonon scattering ,Condensed matter physics ,Nanowire ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,Condensed Matter::Materials Science ,Temperature gradient ,Condensed Matter::Superconductivity ,Scattering rate ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Relaxation (physics) ,Relaxation length ,010306 general physics - Abstract
We study the heat relaxation in current biased metallic films in the regime of strong electron-phonon coupling. A thermal gradient in the direction normal to the film is predicted, with a spatial temperature profile determined by the temperature-dependent heat conduction. In the case of strong phonon scattering the heat conduction occurs predominantly via the electronic system and the profile is parabolic. This regime leads to the linear dependence of the noise temperature as a function of voltage bias, in spite of the fact that all the dimensions of the film are large compared to the electron-phonon relaxation length. This is in stark contrast to the conventional scenario of relaxation limited by the electron-phonon scattering rate. A preliminary experimental study of a 200 nm thick NbN film indicates the relevance of our model for materials used in superconducting nanowire single-photon detectors., accepted in JETP Letters
- Published
- 2020
- Full Text
- View/download PDF
45. Theoretical model for predicting thermoelectric properties of tin chalcogenides
- Author
-
Raveena Gupta, Chandan Bera, Naveen Kumar, and Prabhjot Kaur
- Subjects
Materials science ,Condensed matter physics ,Phonon ,Scattering ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,chemistry ,Scattering rate ,Thermoelectric effect ,symbols ,Figure of merit ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tin ,Carnot cycle - Abstract
The global energy crisis demands the search for new materials for efficient thermoelectric energy conversion. Theoretical predictive modelling with experiments can expedite the global search of novel and ecoconscious thermoelectric materials. The efficiency of thermoelectric materials depends upon the thermoelectric figure of merit (ZT). In this perspective, we discuss the theoretical model to calculate thermoelectric properties. Different scattering mechanisms of electrons and phonons are calculated using a simple model for the fast prediction of thermoelectric properties. Thermoelectric properties based on the simple model have shown more than 90% agreement with the experimental values. Possibility to optimize the figure of merit by alloying, defects, nanostructuring and band convergence is also discussed for layered chalcogenides of tin. In the case of doped materials, ion-impurity scattering is found to be dominating over electron–phonon scattering and the power factor can be optimized by tuning the former scattering rate. For phonon transport, alloy scattering is found to be the most dominating among all other scattering mechanisms. Theoretically, it is found that in the temperature range between 300 K and 800 K, SnSe0.70S0.30 has the highest ZT with an efficiency of 17.20% with respect to Carnot efficiency. There could be 53.8% enhancement of the device efficiency in SnSe0.70S0.30 compared to experimentally reported SnSe0.50S0.50 in the medium temperature range (300 K to 800 K). Possible routes to achieve the best ZT in the medium temperature range are also discussed in this perspective.
- Published
- 2020
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46. Quantification of the Effect of Multiple Scattering on Array Imaging Performance
- Author
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Alexander Velichko
- Subjects
Detection limit ,Materials science ,Acoustics and Ultrasonics ,Scattering ,business.industry ,01 natural sciences ,Rod ,Speckle pattern ,Optics ,Scattering rate ,0103 physical sciences ,Ultrasonic sensor ,Detection theory ,Electrical and Electronic Engineering ,Material properties ,business ,010301 acoustics ,Instrumentation - Abstract
A quantitative assessment of the detection limit is an important task in a range of fields, where imaging in a random scattering medium is performed. All images suffer, to varying extents, from coherent noise including speckle caused by material microstructure. The quality of images can be greatly improved by using phased arrays because of the possibility to focus backscattered signals in transmission and reception. As a consequence, under the single scattering assumption, the signal-to-noise ratio increases with frequency due to better focusing. However, in reality, material structural noise severely affects the detection performance, and especially at high frequencies and large penetration depths. The actual detection limit depends on the type of imaged target and the material properties, but the underlying physical reason is the same and is related to the increase in the contribution of multiple scattering to the measured data. Thus, in this paper a method for estimating the proportion of the multiple scattering contribution in the total image intensity is proposed. Experimental results are presented for ultrasonic array immersion imaging of a collection of randomly distributed steel rods, as well as direct contact imaging of highly scattering polycrystalline materials. It is shown that the signal-to-noise ratio (SNR) as a function of frequency and imaging depth is directly correlated with the measured single scattering rate. Moreover, the detection limit corresponds to the onset of the dominant multiple scattering regime, when the multiple scattering rate approaches 100%.
- Published
- 2020
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47. Hot Electron Relaxation In Ferromagnetic Metals: Memory Function Approach
- Author
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Cem Sevik and Luxmi Rani
- Subjects
Physics ,Condensed matter physics ,Scattering ,Magnon ,Condensed Matter Physics ,Coupling (probability) ,Omega ,Debye frequency ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Scattering rate ,symbols ,Relaxation (physics) ,Condensed Matter::Strongly Correlated Electrons ,Debye model - Abstract
This study leads to the investigation of the non-equilibrium electron relaxation in ferromagnetic metals. Here we consider the relaxation of electrons due to their coupling with magnons and phonons in a ferromagnet using the memory function approach. In the present model, electrons live at a higher temperature than that of the phonon and magnon baths, mimicking a non-equilibrium steady-state situation. Further we analyze theoretically the generalized Drude scattering rate within the framework of two temperature model and study the full frequency and temperature behavior for it. In zero frequency regime, the rate of electron-magnon scattering and electron-phonon scattering shows a linear temperature dependence at higher temperature values greater than Debye temperature. Whereas at lower temperature values, $$T\ll \Theta _{D}$$ , corresponding scattering rates follow the temperature behavior as ( $$1/\tau _{e-p} \varpropto T^3$$ ) and ( $$1/\tau _{e-m} \varpropto T^{3/2}$$ ), respectively. In the AC regime, we compute that $$1/\tau \propto \omega ^2$$ for $$\omega \ll \omega _{D}$$ and for the values greater than the Debye frequency, it is $$\omega$$ -independent. Also, in lower frequency and zero temperature limit, we have observed the different frequency scale of electron-magnon and electron-phonon scattering, i.e., ( $$1/\tau \propto \omega ^{3/2}$$ ) and ( $$1/\tau \propto \omega ^{3}$$ ). These results can be viewed with the pump-probe experimental setting for ferromagnetic metals.
- Published
- 2022
48. Sensitivity of Thermoelectric Properties from the EPA Method and Its Variants on Variations in Phonon Frequencies
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Daehyun Wee, Minkyung Han, Semi Bang, Jeeyoung Kim, and Jiwon Kang
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Physics ,Condensed matter physics ,Phonon ,Scattering ,Condensed Matter Physics ,Thermoelectric materials ,Electronic, Optical and Magnetic Materials ,Brillouin zone ,Condensed Matter::Materials Science ,Condensed Matter::Superconductivity ,Seebeck coefficient ,Scattering rate ,Thermoelectric effect ,Materials Chemistry ,Condensed Matter::Strongly Correlated Electrons ,Charge carrier ,Electrical and Electronic Engineering - Abstract
The electron–phonon coupling phenomenon is an important scattering source of charge carriers in thermoelectric materials. As the result, consideration of the scattering mechanism due to electron–phonon coupling is an essential part of the first-principles prediction methods for thermoelectric properties of materials, i.e., the Seebeck coefficient and electrical conductivity. However, a direct, high-resolution treatment of electron–phonon coupling in a realistic situation is too expensive for practical purposes, and approximation methods have been developed for the phenomena at a reasonable level of computational cost. The electron–phonon averaged (EPA) method and its variants have been recently introduced as such approximation methods. These methods comprise two major approximations. First, the electron–phonon coupling matrix elements, which are explicitly dependent on the momentum of charge carriers and that of scattering phonons, are approximated as a function of two energies only, i.e., the energy of the incoming charge carrier before scattering and that of the outgoing charge carrier after scattering. Second, the phonon frequencies in the formula of scattering rate are replaced with their averages in the Brillouin zone. Although these methods have achieved remarkable successes in predicting thermoelectric properties of materials, uncertainty introduced by these approximations and sensitivity of the results to variations of input parameters in these approximations have not been assessed completely. In this study, the uncertainty and sensitivity of thermoelectric properties, predicted with the EPA method and its variants, on variations in phonon frequencies are investigated. A thermoelectric p-type half-Heusler compound, HfCoSb, is used as an example. An empirical bootstrap method is employed to assess the impact of sampled phonon frequencies during the averaging process, whose results show that the impact of variations in phonon frequencies induces a minor but detectable change in predicted thermoelectric properties.
- Published
- 2019
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49. Scaling and Inelastic Scattering in the Integer Quantum-Hall-Effect
- Author
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Brandes, T., Schweitzer, L., Kramer, B., Cerdeira, Hilda A., editor, Kramer, Bernhard, editor, and Schön, Gerd, editor
- Published
- 1995
- Full Text
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50. Ultrafast carrier’s dynamics with scattering rate saturation in Ge thinfilms
- Author
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Anshika Srivastava, Pankaj Srivastava, Anshu Saxena, Fanish Kumar Gupta, and P.K. Saxena
- Subjects
Physics ,Superposition principle ,Scattering ,Terahertz radiation ,Scattering rate ,Relaxation (physics) ,Spectroscopy ,Ultrashort pulse ,Boltzmann equation ,Computational physics - Abstract
An innovative theoretical approach for deeper understanding of the ultrafast spectroscopy experiments through solution of the Boltzmann transport equation coupled with various nonlinear scattering mechanisms, overcoming the limitations offered by DFT, RT-TDDFT and molecular based methods, is reported. A clear advantage of the real-time approach is that it does not make a priori assumptions about specific scattering, relaxation mechanisms and has capabilities to capture the full real-time carrier’s dynamics, including the superposition of all electron–electron, electron-lattice and electron–phonon scatterings etc. No such method with advances in theoretical treatments to explain ultrafast spectroscopy has been reported previously as per the author’s knowledge.
- Published
- 2021
- Full Text
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