5,319 results on '"Electron-phonon interactions"'
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2. High-temperature threshold of damage of SiC by swift heavy ions
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Zainutdinov, D.I., Borodin, V.A., Gorbunov, S.A., Medvedev, N., Rymzhanov, R.A., Sorokin, M.V., Voronkov, R.A., and Volkov, A.E.
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- 2025
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3. Computational insights to electron-phonon and phonon-phonon interactions in AgX (X = Br, Cl): Refining thermoelectric property predictions
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Brahma, Jeet Kumar, Khalid, Farrukh, and Kalita, Pankaj
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- 2025
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4. A first-principles investigation of structural, dynamical, electronic and phonon-mediated superconducting properties of B3-TMCs (TM=Pd, Pt) using local, semilocal, and nonlocal functionals
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Bakar, Abu, Shahbaz, Muhammad, and Afaq, A.
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- 2025
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5. Quantification of the strong, phonon-induced Urbach tails in β-Ga2O3 and their implications on electrical breakdown.
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Islam, Ariful, Rock, Nathan David, and Scarpulla, Michael A.
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ELECTRIC breakdown , *IMPACT ionization , *ELECTRON-phonon interactions , *LIGHT transmission , *DEFORMATION potential , *ELECTRON impact ionization , *POLARONS - Abstract
In ultrawide bandgap (UWBG) nitride and oxide semiconductors, increased bandgap (Eg) correlates with greater ionicity and strong electron–phonon coupling. This limits mobility through phonon scattering, localizes carriers via polarons and self-trapping, broadens optical transitions via dynamic disorder, and modifies the breakdown field. Herein, we use polarized optical transmission spectroscopy from 77 to 633 K to investigate the Urbach energy (Eu) for many orientations of Fe- and Sn-doped β-Ga2O3 bulk crystals. We find Eu values ranging from 60 to 140 meV at 293 K and that static (structural defects plus zero-point phonons) disorder contributes more to Eu than dynamic (finite temperature phonon-induced) disorder. This is evidenced by lack of systematic Eu anisotropy, and Eu correlating more with x-ray diffraction rocking-curve broadening than with Sn-doping. The lowest measured Eu are ∼10× larger than for traditional semiconductors, pointing out that band tail effects need to be carefully considered in these materials for high field electronics. We demonstrate that, because optical transmission through thick samples is sensitive to sub-gap absorption, the commonly used Tauc extraction of a bandgap from transmission through Ga2O3 >1–3 μm thick is subject to errors. Combining our Eu(T) from Fe-doped samples with Eg(T) from ellipsometry, we extract a measure of an effective electron–phonon coupling that increases in weighted second order deformation potential with temperature and a larger value for E||b than E||c. The large electron–phonon coupling in β-Ga2O3 suggests that theories of electrical breakdown for traditional semiconductors need expansion to account not just for lower scattering time but also for impact ionization thresholds fluctuating in both time and space. [ABSTRACT FROM AUTHOR] more...
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- 2024
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6. Shedding light on evolution of Raman line shape with probing laser power: Light-induced perturbation in electron–phonon coupling.
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Rambadey, Omkar V., Kumar, Kailash, Nain, Ritu, Kumar, Anil, Sagdeo, Pankaj R., Chamberlin, Philip M., and Adu, Kofi W.
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ELECTRON-phonon interactions , *SILICON nanowires , *LASERS , *RAMAN scattering , *RAMAN spectroscopy , *RAMAN effect , *SURFACE temperature , *PHONONS - Abstract
The laser power mediated changes in the Raman line shape have been considered in terms of interference between discrete phonon states ρ and the electronic continuum states ϰ contributed by Urbach tail states. The laser-induced effects are treated in terms of the increase in the surface temperature and thereby the scaling of electronic disorder, i.e., Urbach energy, which can further contribute to the electron–phonon interactions. Therefore, the visualization of this effect is attempted analytically as a perturbation term in the Hamiltonian, which clearly accounts for the observed changes with laser power. This has been investigated based on the experimental results of laser power dependent Raman spectra of bulk EuFeO3 and silicon nanowires, which are found to provide convincing interpretations. [ABSTRACT FROM AUTHOR] more...
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- 2024
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7. Effect of pressure, nitrogen-doping, and lanthanide elements substitution on the superconductivity of rocksalt-type LuH.
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Jiang, Kai-Yue, Chen, Ying-Jie, and Lu, Hong-Yan
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SUPERCONDUCTING transition temperature , *NITROGEN , *SUPERCONDUCTIVITY , *ELECTRON-phonon interactions , *DENSITY functional theory , *FERMI level - Abstract
The report on near-ambient superconductivity in nitrogen-doped lutetium hydride is still under controversy. Here, guided by x-ray diffraction data of nitrogen-doped lutetium hydride, we choose a possible cubic superconducting phase named rocksalt-type LuH (RS-LuH) and study the superconductivity of pristine RS-LuH, nitrogen-doped RS-LuH named Lu 4 NH 3 , and lanthanide elements substitution of RS-LuH at pressures 0, 1, and 10 GPa by performing density functional theory and isotropic Eliashberg equation. As pressure increases from 0 to 10 GPa, all phonon spectra notably harden, resulting in the suppression of electron–phonon coupling. Moreover, the decrease in superconducting critical temperature (T c) of Lu 4 NH 3 is due to the reduction of electron–phonon coupling and the density of states at the Fermi level compared with pristine RS-LuH. Finally, our investigation reveals a monotonic increase in T c with ascending atomic numbers via lanthanide element substitution. Notably, RS-LuH exhibits the highest T c (T c = 19.7 K) among all compounds we studied. Therefore, our theoretical exploration enriches the understanding of the superconductivity in nitrogen-doped lutetium hydride under varying pressures. [ABSTRACT FROM AUTHOR] more...
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- 2024
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8. Acoustic phonon excitation in gold probed by time-resolved photoemission electron microscopy.
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Jiang, Pengzuo, Zhang, Linfeng, Zheng, Wei, Wang, Yang, Liu, Yu, Xiao, Jingying, Li, Yaolong, Medvedev, Nikita, Ischenko, Anatoly, Kang, Zexin, Liu, Yunquan, Li, Zheng, and Wu, Chengyin
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ACOUSTIC phonons , *ACOUSTIC excitation , *ELECTRON-phonon interactions , *ELECTRON microscopy , *PHOTOEMISSION , *ENERGY transfer - Abstract
Electron–phonon coupling is an important energy transfer mechanism in solids after ultrafast laser excitation. In this study, we present an extreme ultraviolet (EUV) and infrared (IR) pump-probe photoemission experiment to investigate the electron–phonon coupling in nonequilibrium gold. The energy of IR-laser-emitted photoelectrons is shifted due to the EUV photoemission and oscillates with a ∼ 4 T H z frequency. Such oscillation is considered as the effective excitation of the longitudinal acoustic phonon mode in gold through the spectral-dependent electron–phonon coupling. Our study showcases the capability of time-resolved photoemission electron microscopy to monitor the non-equilibrium lattice vibrations with ultrahigh spatial and temporal resolution. [ABSTRACT FROM AUTHOR] more...
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- 2024
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9. Anharmonic and quantum effects in Pm3̄ AlM(M = Hf, Zr)H6 under high pressure: A first-principles study.
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Hou, Pugeng, Ma, Yao, Pang, Mi, Cai, Yongmao, Shen, Yuhua, Xie, Hui, and Tian, Fubo
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SUPERCONDUCTING transition temperature , *LATTICE dynamics , *CRYSTAL lattices , *ELECTRON-phonon interactions , *QUANTUM fluctuations - Abstract
First-principles calculations were employed to investigate the impact of quantum ionic fluctuations and lattice anharmonicity on the crystal structure and superconductivity of Pm 3 ̄ AlM(M = Hf, Zr)H6 at pressures of 0.3–21.2 GPa (AlHfH6) and 4.7–39.5 GPa (AlZrH6) within the stochastic self-consistent harmonic approximation. A correction is predicted for the crystal lattice parameters, phonon spectra, and superconducting critical temperatures, previously estimated without considering ionic fluctuations on the crystal structure and assuming the harmonic approximation for lattice dynamics. The findings suggest that quantum ionic fluctuations have a significant impact on the crystal lattice parameters, phonon spectra, and superconducting critical temperatures. Based on our anharmonic phonon spectra, the structures will be dynamically stable at 0.3 GPa for AlHfH6 and 6.2 GPa for AlZrH6, ∼6 and 7 GPa lower than pressures given by the harmonic approximation, respectively. Due to the anharmonic correction of their frequencies, the electron–phonon coupling constants (λ) are suppressed by 28% at 11 GPa for AlHfH6 and 22% at 30 GPa for AlZrH6, respectively. The decrease in λ causes Tc to be overestimated by ∼12 K at 11 GPa for AlHfH6 and 30 GPa for AlZrH6. Even if the anharmonic and quantum effects are not as strong as those of Pm 3 ̄ n-AlH3, our results also indicate that metal hydrides with hydrogen atoms in interstitial sites are subject to anharmonic effects. Our results will inevitably stimulate future high-pressure experiments on synthesis, structural, and conductivity measurements. [ABSTRACT FROM AUTHOR] more...
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- 2024
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10. The origins of dual-peak emission and anomalous exciton decay in 2D Sn-based perovskites.
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Wang, Xinrui, Wei, Yingqiang, Kuang, Zhiyuan, Wang, Xing, Dai, Mian, Li, Xiuyong, Lu, Runqing, Liu, Wang, Chang, Jin, Ma, Chao, Huang, Wei, Peng, Qiming, and Wang, Jianpu
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PEROVSKITE , *ELECTRON-phonon interactions , *ELECTRON-hole recombination , *X-ray diffraction measurement , *BINDING energy , *NEUTRINOLESS double beta decay - Abstract
Two-dimensional (2D) Sn-based perovskites exhibit significant potential in diverse optoelectronic applications, such as on-chip lasers and photodetectors. Yet, the underlying mechanism behind the frequently observed dual-peak emission in 2D Sn-based perovskites remains a subject of intense debate, and there is a lack of research on the carrier dynamics in these materials. In this study, we investigate these issues in a representative 2D Sn-based perovskite, namely, PEA2SnI4, through temperature-, excitation intensity-, angle-, and time-dependent photoluminescence studies. The results indicate that the high- and low-energy peaks originate from in-face and out-of-face dipole transitions, respectively. In addition, we observe an anomalous increase in the non-radiative recombination rate as temperature decreases. After ruling out enhanced electron–phonon coupling and Auger recombination as potential causes of the anomalous carrier dynamics, we propose that the significantly increased exciton binding energy (Eb) plays a decisive role. The increased Eb arises from enhanced electronic localization, a consequence of weakened lattice distortion at low temperatures, as confirmed by first-principles calculations and temperature-dependent x-ray diffraction measurements. These findings offer valuable insights into the electronic processes in the unique 2D Sn-based perovskites. [ABSTRACT FROM AUTHOR] more...
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- 2024
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11. Electron–phonon interaction-driven dynamic conductivity in monolayer phosphorene with broken inversion symmetry.
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Yar, Abdullah and Sultana, Rifat
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ELECTRON-phonon interactions , *OPTICAL conductivity , *PHOSPHORENE , *MONOMOLECULAR films , *PHONONS , *SYMMETRY breaking , *RENORMALIZATION (Physics) - Abstract
Electronic transport in inversion symmetry broken monolayer phosphorene under the influence of electron–phonon interaction is investigated. Such interaction renormalizes the band structure, leading to a significant modification of electron dynamics, which depends on the interaction strength. We find that the imaginary part of the self-energy remains minimal within a particular region of energy ℏ ω , where the quasiparticle has zero density of final states. It turns out that the emission of phonon is not allowed in that energy range. At the boundary of this region, there is a sudden increase in the imaginary part of the self-energy, where its real part exhibits singular behavior around specific energies. In addition, it is shown that dynamic optical conductivity exhibits remarkable effects in the presence of the electron–phonon interaction. In particular, it remains minimal in a particular region of energy ℏ ω , then it increases monotonically and hits the peak of the main absorption edge. Moreover, we find that the dynamic optical conductivity changes significantly with the change in electron–phonon interaction strength, temperature, phonon energy, chemical potential, and bandgap in the energy spectrum of the system. Both the real and imaginary parts of the self-energy acquire energy dependence that reflects phonon structure and leads to a shift in the conductivity peak of the longitudinal optical conductivity. [ABSTRACT FROM AUTHOR] more...
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- 2024
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12. Strong electron–phonon coupling and multigap superconductivity in 2H/1T Janus MoSLi monolayer.
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Xie, Hongmei, Huang, Zhijing, Zhao, Yinchang, Huang, Hao, Li, Geng, Gu, Zonglin, and Zeng, Shuming
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ELECTRON-phonon interactions , *SUPERCONDUCTIVITY , *CHARGE density waves , *SUPERCONDUCTING transition temperature , *COUPLING constants , *MIRROR symmetry - Abstract
Two-dimensional (2D) Janus transition metal dichalcogenides MXY manifest novel physical properties owing to the breaking of out-of-plane mirror symmetry. Recently, the 2H phase of MoSH has been demonstrated to possess intrinsic superconductivity, whereas the 1T phase exhibits a charge density waves state. In this paper, we have systematically studied the stability and electron–phonon interaction characteristics of MoSLi. Our results have shown that both the 2H and 1T phases of MoSLi are stable, as indicated by the phonon spectrum and the ab initio molecular dynamics. However, the 1T phase exhibits an electron–phonon coupling constant that is twice as large as that of the 2H phase. In contrast to MoSH, the 1T phase of MoSLi exhibits intrinsic superconductivity. By employing the ab initio anisotropic Migdal-Eliashberg formalism, we have revealed the two-gap superconducting nature of 1T-MoSLi, with a transition temperature (Tc) of 14.8 K. The detailed analysis indicates that the superconductivity in 1T-MoSLi primarily originates from the interplay between the vibration of the phonon modes in the low-frequency region and the dz2 orbital. These findings provide a fresh perspective on superconductivity within Janus structures. [ABSTRACT FROM AUTHOR] more...
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- 2024
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13. Novel hard and unusual superconducting monoclinic phase of FeB2C2: An ab initio evolutionary study.
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Kotmool, Komsilp, Pinsook, Udomsilp, Luo, Wei, Ahuja, Rajeev, and Bovornratanaraks, Thiti
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ELECTRON-phonon interactions , *HARD materials , *PHASE space , *VICKERS hardness , *SPACE groups - Abstract
This study focuses on conducting an ab initio evolutionary investigation to search for stable polymorphs of iron diborocarbides with the formula FeB 2 C 2. We also examined other forms of C contents, including FeB 3 C and FeBC 3. Our findings reveal that the lowest energetic structure of FeB 2 C 2 is a semimetallic monoclinic phase with a space group (s.g.) of C2/m and a metastable metallic phase of FeB 2 C 2 is an orthorhombic structure with s.g. of Pmmm. In addition, structural and relative properties of FeB 3 C and FeBC 3 are performed and discussed to compare with FeB 2 C 2. All predicted structures are dynamically and elastically stable, verified without negative phonon frequency and Born criteria, respectively. We also analyzed the energetic stability through calculated cohesive and formation energies, which showed that C2/m- FeB 2 C 2 is stable at low pressure. Interestingly, the C2/m and Pmmm phases of FeB 2 C 2 are hard materials with Vickers hardness ( H v) of 22.40 and 27.52 GPa, respectively. Additionally, we examined the electron–phonon coupling of both FeB 2 C 2 phases. Unexpectedly, we found that the semimetallic C2/m- FeB 2 C 2 phase is a superconductor with a significant superconducting temperature ( T c) exceeding 6 K. These findings provide some novel results for the Fe–B–C system and pave the way for investigating other metal borocarbides and related ternary compounds. [ABSTRACT FROM AUTHOR] more...
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- 2024
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14. Impacts of hot electron diffusion, electron–phonon coupling, and surface atoms on metal surface dynamics revealed by reflection ultrafast electron diffraction.
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He, Xing, Ghosh, Mithun, and Yang, Ding-Shyue
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ELECTRON-phonon interactions , *HOT carriers , *ELECTRON diffraction , *SURFACE dynamics , *METALLIC surfaces , *ELECTRON diffusion - Abstract
Metals exhibit nonequilibrium electron and lattice subsystems at transient times following femtosecond laser excitation. In the past four decades, various optical spectroscopy and time-resolved diffraction methods have been used to study electron–phonon coupling and the effects of underlying dynamical processes. Here, we take advantage of the surface specificity of reflection ultrafast electron diffraction (UED) to examine the structural dynamics of photoexcited metal surfaces, which are apparently slower in recovery than predicted by thermal diffusion from the profile of absorbed energy. Fast diffusion of hot electrons is found to critically reduce surface excitation and affect the temporal dependence of the increased atomic motions on not only the ultrashort but also sub-nanosecond times. Whereas the two-temperature model with the accepted physical constants of platinum can reproduce the observed surface lattice dynamics, gold is found to exhibit appreciably larger-than-expected dynamic vibrational amplitudes of surface atoms while keeping the commonly used electron–phonon coupling constant. Such surface behavioral difference at transient times can be understood in the context of the different strengths of binding to surface atoms for the two metals. In addition, with the quantitative agreements between diffraction and theoretical results, we provide convincing evidence that surface structural dynamics can be reliably obtained by reflection UED even in the presence of laser-induced transient electric fields. [ABSTRACT FROM AUTHOR] more...
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- 2024
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15. Magnetothermal properties of CoO2 monolayer from first-principles and Monte Carlo simulations.
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Xu, Xing-Long, Hu, Cui-E., Wu, Hao-Jia, Geng, Hua-Yun, and Chen, Xiang-Rong
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MONOMOLECULAR films , *MONTE Carlo method , *STRUCTURAL stability , *CARRIER density , *ELECTRON-phonon interactions , *COBALT oxides , *BAND gaps , *THERMAL properties - Abstract
Cobalt oxides are known for their excellent heat transfer properties. The main component of cobalt oxides is the CoO2 monolayer, which exhibits high-temperature superconductivity caused by strong electron–phonon coupling (EPC). We here systematically investigate the structural stability, electronic structure, and magnetism of the CoO2 monolayer using first-principles and Monte Carlo simulations. On this basis, we further study the changes in the spin energy gap, magnetic axis direction, and other properties of the CoO2 monolayer with the changes in carrier concentration. By appropriately doping the CoO2 monolayer with holes, the magnetic axis direction of the CoO2 monolayer can be reversed, thereby enhancing its potential application in the field of spin electronic devices. Monte Carlo simulation is used to study the regulation of different factors on the magnetothermal properties of the CoO2 monolayer. Through the analysis of physical parameters such as Curie temperature (TC) and bandgap, we find that the appropriate carrier concentration and magnetic field can not only regulate the magnetothermal properties of materials but also further improve the efficiency of materials in low-temperature environments. [ABSTRACT FROM AUTHOR] more...
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- 2024
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16. Photoluminescence studies of the charge states of nitrogen vacancy centers in diamond after arsenic ion implantation and subsequent annealing.
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Huangfu, Chenyang, Zhang, Yufei, Hao, Jinchen, Jia, Gangyuan, Wu, Haitao, Wang, Xujie, Wang, Wei, and Wang, Kaiyue
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ION implantation , *ARSENIC , *ELECTRON-hole recombination , *ELECTRON-phonon interactions , *DIAMONDS , *REDSHIFT - Abstract
In this work, nitrogen vacancy (NV) centers of high nitrogen diamond implanted with arsenic ions were investigated by photoluminescence spectroscopy. The transition of the NV center charge state was discussed by the regularly changing laser excitation power and measurement temperature following high-temperature annealing. After high-temperature annealing, the amorphous layer generated by arsenic ion implantation is transformed into a graphitization layer, resulting in a decrease in the NV yield. The electric neutral NV (NV0) center and negatively charged NV (NV−) center are affected by both radiation recombination and Auger recombination with increasing laser power. Accompanied by the increasing measurement temperature, the intensities of NV centers gradually decreased and eventually quenched. In addition, the charge states of NV− and NV0 centers were undergoing a transition. The zero phonon line positions of NV centers were also red shift, it was attributed to the dominant role of electron–phonon interaction in the temperature-dependent displacement of diamond energy gaps. The full width at half maxima of NV center were broadened significantly at higher temperatures. [ABSTRACT FROM AUTHOR] more...
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- 2024
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17. Transient simulation of the electrical hysteresis in a metal/polymer/metal nanostructure.
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Hao, Yutong, Lu, Qiuxia, Zhang, Yalin, Zhang, Maomao, Liu, Xiaojing, and An, Zhong
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ELECTRIC transients , *ELECTRON-phonon interactions , *EQUATIONS of motion , *CONDUCTING polymers , *CURRENT-voltage characteristics , *HYSTERESIS loop , *HYSTERESIS - Abstract
The time-dependent quantum transportation through a metal/polymer/metal system is theoretically investigated on the basis of a Su–Schrieffer–Heeger model combined with the hierarchical equations of motion formalism. Using a non-adiabatic dynamical method, the evolution of the electron subspace and lattice atoms with time can be obtained. It is found that the calculated transient currents vary with time and reach stable values after a response time under the bias voltages. However, the stable current as the system reaches its dynamical steady state exhibits a discrepancy between two sweep directions of the bias voltage, which results in pronounced electrical hysteresis loops in the current–voltage curve. By analyzing the evolution of instantaneous energy eigenstates, the occupation number of the instantaneous eigenstates, and the lattice of the polymer, we show that the formation of excitons and the delay of their annihilation are responsible for the hysteretic current–voltage characteristics, where electron–phonon interactions play the key factor. Furthermore, the hysteresis width and amplitude can also be modulated by the strength of the electron–phonon coupling, level-width broadening function, and temperature. We hope these results about past condition-dependent switching performance at a sweep voltage can provide further insight into some of the basic issues of interest in hysteresis processes in conducting polymers. [ABSTRACT FROM AUTHOR] more...
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- 2024
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18. Predictions of thorium super nitrides and superconductivity under pressure: Ab initio calculations.
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Sahoo, B. D. and Joshi, K. D.
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AB-initio calculations , *NITRIDES , *SUPERCONDUCTIVITY , *ELECTRON-phonon interactions , *PHASE diagrams , *THORIUM - Abstract
Thorium nitrides have been the topic of intense studies due to their prospective applications as advanced nuclear fuels. The phase diagram of the Th–N scheme, however, continues unknown at low temperatures and extremely high pressures. In this article, we examine the Th–N system's phase diagram up to 300 GPa from the first-principle approach using universal structure predictor: evolutionary Xtallography (USPEX) method. Apart from the experimentally observed phase (ThN, Th2N3, and Th3N4), there are several unique chemical stoichiometries, i.e., ThN3, ThN4, ThN6, ThN8, ThN10, and ThN12 are found to have stability fields on the Th–N phase diagram at pressure of 3.0, 32, 100, 42, 28, and 236 GPa along with previously predicted composition ThN2 at 3.5 GPa. The structural stability of the predicted compositions is further assessed by evaluating the elastic and dynamic stability. Out of all above mentioned compositions, ThN3 is possibly a metastable one at 0 GPa. Electronic structure calculations predict that all newly discovered compositions are metallic except ThN10, which is semi-metallic at high pressures. Further, we predict that ThN4 and ThN6 have high electron–phonon coupling constant of 1.874 and 0.894 with Tc around 21.22 and 25.02 K, respectively, at 100 GPa. [ABSTRACT FROM AUTHOR] more...
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- 2024
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19. Hot carrier relaxation dynamics of an aza-covalent organic framework during photoexcitation: An insight from ab initio quantum dynamics.
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Ghosh, Atish, Das, Priya, Kumar, Subhash, and Sarkar, Pranab
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HOT carriers , *QUANTUM theory , *ELECTRON-phonon interactions , *ELECTRON-hole recombination , *PHOTOEXCITATION - Abstract
In order to develop an efficient metal-free solar energy harvester, we herein performed the electronic structure calculation, followed by the hot carrier relaxation dynamics of two dimensional (2D) aza-covalent organic framework by time domain density functional calculations in conjunction with non-adiabatic molecular dynamics (NAMD) simulation. The electronic structure calculation shows that the aza-covalent organic framework (COF) is a direct bandgap semiconductor with acute charge separation and effective optical absorption in the UV-visible region. Our study of non-adiabatic molecular dynamics simulation predicts the sufficiently prolonged electron–hole recombination process (6.8 nanoseconds) and the comparatively faster electron (22.48 ps) and hole relaxation (0.51 ps) dynamics in this two-dimensional aza-COF. According to our theoretical analysis, strong electron–phonon coupling is responsible for the rapid charge relaxation, whereas the electron–hole recombination process is slowed down by relatively weak electron–phonon coupling, relatively lower non-adiabatic coupling, and quick decoherence time. We do hope that our results of NAMD simulation on exciton relaxation dynamics will be helpful for designing photovoltaic devices based on this two dimensional aza-COF. [ABSTRACT FROM AUTHOR] more...
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- 2024
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20. First-principles calculations of defects and electron–phonon interactions: Seminal contributions of Audrius Alkauskas to the understanding of recombination processes.
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Zhang, Xie, Turiansky, Mark E., Razinkovas, Lukas, Maciaszek, Marek, Broqvist, Peter, Yan, Qimin, Lyons, John L., Dreyer, Cyrus E., Wickramaratne, Darshana, Gali, Ádám, Pasquarello, Alfredo, and Van de Walle, Chris G. more...
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ELECTRON-phonon interactions , *OPTOELECTRONIC devices , *ELECTRONIC equipment , *ELECTRONIC materials - Abstract
First-principles calculations of defects and electron–phonon interactions play a critical role in the design and optimization of materials for electronic and optoelectronic devices. The late Audrius Alkauskas made seminal contributions to developing rigorous first-principles methodologies for the computation of defects and electron–phonon interactions, especially in the context of understanding the fundamental mechanisms of carrier recombination in semiconductors. Alkauskas was also a pioneer in the field of quantum defects, helping to build a first-principles understanding of the prototype nitrogen-vacancy center in diamond, as well as identifying novel defects. Here, we describe the important contributions made by Alkauskas and his collaborators and outline fruitful research directions that Alkauskas would have been keen to pursue. Audrius Alkauskas' scientific achievements and insights highlighted in this article will inspire and guide future developments and advances in the field. [ABSTRACT FROM AUTHOR] more...
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- 2024
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21. Phonon-assisted carrier transport and indirect optical absorption of cubic boron nitride from first-principles.
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Iqbal, Safdar, Cheng, Tao, Duan, Xinlei, Liu, Linhua, and Yang, Jia-Yue
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BORON nitride , *BOLTZMANN'S equation , *LIGHT absorption , *ELECTRON mobility , *CHARGE carrier mobility , *ELECTRON-phonon interactions - Abstract
Inquiring the isotopically engineered carrier transport in polar materials remains an open question. Herein, the phonon-limited drift carrier mobility of single-crystal cubic boron nitride is presented using first-principles calculations. Natural c-BN has the predicted electron mobility of 1230 and 760 cm2/V s by solving the iterative Boltzmann transport equation and self-energy relaxation time approximation, respectively. The hole mobility under the Boltzmann transport equation and self-energy relaxation time approximation is 193 and 105 cm2/Vs, respectively. Subsequently, the electron and hole mobilities at the stable isotope levels of boron and nitride are predicted, and nitride isotopes are found to be more effective than boron for carrier mobility. Those carrier mobilities further decrease with increasing temperature due to the strengthened electron–phonon interactions. Moreover, the phonon-assisted indirect optical absorption of c-BN is investigated by considering the contribution of phonons to the indirect electronic inter-band transitions. The predicted imaginary part of the dielectric function is in better agreement with previous experiments. This work aims to understand the role of phonons in determining the carrier mobility and indirect optical absorption of c-BN. [ABSTRACT FROM AUTHOR] more...
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- 2024
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22. Thickness-dependent polaron crossover in tellurene.
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Kunyan Zhang, Chuliang Fu, Kelly, Shelly, Liangbo Liang, Seoung-Hun Kang, Jing Jiang, Ruifang Zhang, Yixiu Wang, Gang Wan, Siriviboon, Phum, Mina Yoon, Ye, Peide D., Wenzhuo Wu, Mingda Li, and Shengxi Huang more...
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ELECTRON-phonon interactions , *QUASIPARTICLES , *PHONONS , *ELECTRONIC structure , *SUPERCONDUCTIVITY , *POLARONS - Abstract
Polarons, quasiparticles from electron-phonon coupling, are crucial for material properties including high-temperature superconductivity and colossal magnetoresistance. However, scarce studies have investigated polaron formation in low-dimensional materials with phonon polarity and electronic structure transitions. In this work, we studied polarons of tellurene, composed of chiral Te chains. The frequency and linewidth of the A1 phonon, which becomes increasingly polar for thinner tellurene, change abruptly for thickness below 10 nanometers, where field-effect mobility drops rapidly. These phonon and transport signatures, combined with phonon polarity and band structure, suggest a crossover from large polarons in bulk tellurium to small polarons in few-layer tellurene. Effective field theory considering phonon renormalization in the small-polaron regime semiquantitatively reproduces the phonon hardening and broadening effects. This polaron crossover stems from the quasi-one-dimensional nature of tellurene, where modulation of interchain distance reduces dielectric screening and promotes electron-phonon coupling. Our work provides valuable insights into the influence of polarons on phononic, electronic, and structural properties in low-dimensional materials. [ABSTRACT FROM AUTHOR] more...
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- 2025
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23. Regulating Electron‐Phonon Coupling by Solid Additive for Efficient Organic Solar Cells.
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Ge, Zhongwei, Qiao, Jiawei, Li, Yun, Song, Jiali, Duan, Xiaopeng, Fu, Zhen, Hu, Haixia, Yang, Renqiang, Yin, Hang, Hao, Xiaotao, and Sun, Yanming
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ELECTRON-phonon interactions , *SOLAR cells , *PHONON scattering , *SOLIDS , *ADDITIVES - Abstract
Strong electron‐phonon coupling can hinder exciton transport and induce undesirable non‐radiative recombination, resulting in a shortened exciton diffusion distance and constrained exciton dissociation in organic solar cells (OSCs). Therefore, suppressing electron‐phonon coupling is crucially important for achieveing high‐performance OSCs. Here, we employ the solid additive to regulating electron‐phonon coupling in OSCs. The planar configuration of SA1 confers a significant advantage in suppressing lattice vibrations in the active layers, reducing the scattering of excitons by phonons. Consequently, a slow but sustained hole transfer process is identified in the SA1‐assisted film, indicating an enhancement in hole transfer efficiency. Prolonged exciton diffusion length and exciton lifetime are achieved in the blend film processed with SA1, attributed to a low non‐radiative recombination rate and low energetic disorder for charge carrier transport. As a result, a high efficiency of 20 % was achieved for ternary device with a remarkable short‐circuit current. This work highlights the important role of suppressing electron‐phonon coupling in improving the photovoltaic performance of OSCs. [ABSTRACT FROM AUTHOR] more...
- Published
- 2025
- Full Text
- View/download PDF
24. Superconductivity in ordered Li–Al–B compounds.
- Author
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Hussain, K., Donaldson, S. J., Karaca, E., Byrne, P. J. P., Hasnip, P. J., and Probert, M. I. J.
- Subjects
- *
ELECTRON-phonon interactions , *SUPERCONDUCTIVITY , *ENGINEERING - Abstract
Using first principles calculations, we show that materials have strong electron-phonon coupling, with many having a superconducting critical temperature () that exceeds that of the more familiar at ambient pressure. In particular, we find that is the most stable member of the family, with whilst the peak is with which has . Our results reveal that these materials are both thermodynamically and dynamically stable, with strong electron-phonon coupling, indicating significant potential for practical superconducting applications. [ABSTRACT FROM AUTHOR] more...
- Published
- 2025
- Full Text
- View/download PDF
25. Conduction band nonparabolicity, chemical potential, and carrier concentration of intrinsic InSb as a function of temperature.
- Author
-
Zollner, Stefan, Armenta, Carlos A., Yadav, Sonam, and Menéndez, José
- Subjects
ELECTRON-phonon interactions ,THERMAL expansion ,SPHALERITE ,CHEMICAL potential ,CONDUCTION bands - Abstract
In this review, the nonparabolicity of the light-hole and electron bands at the Γ -point in cubic diamond or zinc blende semiconductors is derived from Kane's 8 × 8 k → ⋅ p → model in the large spin–orbit splitting approximation. Examples of several approximations are given with InSb as an example, and their accuracy is discussed. To determine the temperature dependence of the effective masses and the nonparabolicity parameters, the unrenormalized bandgap must be utilized. This includes only the redshift of the bandgap due to thermal expansion, not the renormalization due to deformation-potential electron-phonon coupling. As an application of this method, the chemical potential and the charge carrier concentration of intrinsic InSb are calculated from 50 to 800 K and compared with electrical and optical experiments. These results are also relevant for other semiconductors with small bandgaps as needed for mid-infrared detector applications. [ABSTRACT FROM AUTHOR] more...
- Published
- 2025
- Full Text
- View/download PDF
26. Multiphase superconductivity in PdBi2.
- Author
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Powell, Lewis, Kuang, Wenjun, Hawkins-Pottier, Gabriel, Jalil, Rashid, Birkbeck, John, Jiang, Ziyi, Kim, Minsoo, Zou, Yichao, Komrakova, Sofiia, Haigh, Sarah, Timokhin, Ivan, Balakrishnan, Geetha, Geim, Andre K., Walet, Niels, Principi, Alessandro, and Grigorieva, Irina V. more...
- Subjects
PHASE transitions ,PHYSICAL sciences ,TUNNELING spectroscopy ,SPIN-orbit interactions ,ELECTRON-phonon interactions ,SUPERCONDUCTING transitions ,IRON-based superconductors - Abstract
Unconventional superconductivity, where electron pairing does not involve electron-phonon interactions, is often attributed to magnetic correlations in a material. Well known examples include high-T
c cuprates and uranium-based heavy fermion superconductors. Less explored are unconventional superconductors with strong spin-orbit coupling, where interactions between spin-polarised electrons and external magnetic field can result in multiple superconducting phases and field-induced transitions between them, a rare phenomenon in the superconducting state. Here we report a magnetic-field driven phase transition in β-PdBi2 , a layered non-magnetic superconductor. Our tunnelling spectroscopy on thin PdBi2 monocrystals incorporated in planar superconductor-insulator-normal metal junctions reveals a marked discontinuity in the superconducting properties with increasing in-plane field, which is consistent with a transition from conventional (s-wave) to nodal pairing. Our theoretical analysis suggests that this phase transition may arise from spin polarisation and spin-momentum locking caused by locally broken inversion symmetry, with p-wave pairing becoming energetically favourable in high fields. Our findings also reconcile earlier predictions of unconventional multigap superconductivity in β-PdBi2 with previous experiments where only a single s-wave gap could be detected. β-PdBi2 superconducting properties have been known about since the 1950s, with various works since then indicating the possibility of multiple superconducting gaps and unconventional superconductivity. However, so far only a single gap s-wave superconductivity was detected. Here, using tunnelling spectroscopy under an applied magnetic field, Powell et al observe a transition from s-wave to nodal pairing. [ABSTRACT FROM AUTHOR] more...- Published
- 2025
- Full Text
- View/download PDF
27. Acoustic Phonon Scattering in Free‐Standing Anisotropic Silicon Plates.
- Author
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Mori, Nobuya
- Subjects
- *
ACOUSTIC phonons , *DEFORMATION potential , *PSEUDOPOTENTIAL method , *ELECTRON mobility , *QUANTUM wells - Abstract
The electron–acoustic‐phonon interaction in a free‐standing anisotropic Si plate with (001) surface is studied taking into account the elastic anisotropy of the Si crystal and the modulated phonon modes. The interaction potential is derived from the modulated phonon modes and the anisotropic deformation potential constants. The effective deformation potential constant
D ac is then calculated considering only the lowest electronic sub‐band. In the quantum well model for the electronic states, it is shown that the effective deformation potential for the modulated phonons in an anisotropic Si plate becomesD ac ≈ 13 eV in the thinner region of the plate thickness w≲3.2 nm$w \leq 3.2 \textrm{ } \textrm{ } \text{nm}$. It is also shown that both the phonon modulation and the crystal anisotropy have non‐negligible effects on the effective deformation potential and electron mobility. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
28. Synthesis of CuO/Fe3O4 Nanocomposite for enhanced solar thermal desalination.
- Author
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Fouad, S.S., Nabil, M., Horia, F., Easawi, K., and Negm, S.
- Subjects
- *
IRON oxides , *PHOTOACOUSTIC spectroscopy , *ELECTRON-phonon interactions , *MAGNETIC nanoparticles , *OPTICAL conductivity - Abstract
Nanoparticle (NPs) have attracted the attention of scientists and researchers in water remediation due to the improvement in its processability, and its cost effectiveness. The present work analyzed the synergistic effect of CuO (NPs) with different ratios (0, 0.5, 0.6, 0.7, 0.8, 0.9 and 1 wt %) on the structural, and optical properties of Fe 3 O 4 (NPs), that can be used in water desalination process. The general methodology for preparation and structural properties of CuO (NPs), Fe 3 O 4 (NPs) and CuO/Fe 3 O 4 (NCs) were analyzed by (XRD) and (TEM) measurements. The morphological combination of (SEM) with (EDX), were used for determining the elemental identification of CuO/Fe 3 O 4 (NCs). The characterization topography was found to be strongly affected by the change of the CuO concentration. Furthermore, the Urbach energy (E U ) , steepness parameter (σ) , electron-phonon interaction (E e-p ) , optical band gap (E g ) , refractive index (n) and optical conductivity (σ opt ) were calculated. The optical absorption studies in the UV–Visible region, revealed that the CuO/Fe 3 O 4 (NCs) was found to be direct allowed transition, and the energy bandgap value decreased from 2.52 eV to 2.15 eV based on the percentage change of CuO (NPs) in CuO/Fe 3 O 4 (NCs). Moreover, the value of thermal conductivity (k) , and thermal efficiency ( η ), showed an increase with the increase of the ratio of CuO (NPs), which may be an indication for opening an innovation way that can satisfy the need of seawater desalination technology. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
29. Colossal magnetoresistance from spin-polarized polarons in an Ising system.
- Author
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Ying-Fei Li, Been, Emily M., Balguri, Sudhaman, Chun-Jing Jia, Mahendru, Mira B., Zhi-Cheng Wang, Yi Cui, Su-Di Chen, Makoto Hashimoto, Dong-Hui Lu, Moritz, Brian, Zaanen, Jan, Tafti, Fazel, Devereaux, Thomas P., and Zhi-Xun Shen more...
- Subjects
- *
MAGNETIC transitions , *PHOTOELECTRON spectroscopy , *ELECTRON-phonon interactions , *CONDENSED matter , *DENSITY functional theory - Abstract
Recent experiments suggest a new paradigm toward novel colossal magnetoresistance (CMR) in a family of materials EuM2X2 (M = Cd, In, Zn; X = P, As), distinct from the traditional avenues involving Kondo-Ruderman-Kittel-Kasuya-Yosida crossovers, magnetic phase transitions with structural distortions, or topological phase transitions. Here, we use angle-resolved photoemission spectroscopy and density functional theory calculations to explore their origin, particularly focusing on EuCd2P2. While the low-energy spectral weight royally tracks that of the resistivity anomaly near the temperature with maximum magnetoresistance (TMR) as expected from transport-spectroscopy correspondence, the spectra are completely incoherent and strongly suppressed with no hint of a Landau quasiparticle. Using systematic material and temperature dependence investigation complemented by theory, we attribute this nonquasiparticle caricature to the strong presence of entangled magnetic and lattice interactions, a characteristic enabled by the p-f mixing. Given the known presence of ferromagnetic clusters, this naturally points to the origin of CMR being the scattering of spin-polarized polarons at the boundaries of ferromagnetic clusters. These results are not only illuminating to investigate the strong correlations and topology in EuCd2X2 family, but, in a broader view, exemplify how multiple cooperative interactions can give rise to extraordinary behaviors in condensed matter systems. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
30. Proposed hydrogen kagome metal with charge density wave state and enhanced superconductivity.
- Author
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Liu, Zhao, Liu, Zhonghao, Zhuang, Quan, Ying, Jianjun, and Cui, Tian
- Subjects
CHARGE density waves ,FERMI surfaces ,SCIENTIFIC method ,ELECTRON-phonon interactions ,ELECTRON pairs ,SUPERCONDUCTING transition temperature - Abstract
The d-transition kagome metals provide a novel platform for exploring correlated superconducting state intertwined with charge ordering. However, the force of charge-density-wave (CDW) and superconductivity (SC) formation, and the mechanism underlying electron pairing remain elusive. Here, utilizing our newly developed methodology based on electride states as fingerprints, we propose a novel class of hydrogen-kagome superconductors AH
3 Li5 (A = C, Si, P) with ideal kagome band characteristics and elucidate the electron-phonon coupling (EPC) mechanism responsible for electron pairing. The representative compressed PH3 Li5 and CH3 Li5 demonstrates impressive superconducting transition temperatures (Tc s) of 120.09 K and 57.18 K, respectively. Importantly, the CDW competes with SC thus resulting in a pressure-driven dome-shaped SC in CH3 Li5 , where the CDW order was induced by both EPC and Fermi surface nesting. Our study presents a scientific method for identifying high-Tc hydrogen-kagome metals and provides new avenues to fundamentally understand the underlying mechanism of CDW and SC, thereby guiding future experimental investigations. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
31. Electron transport in one-dimensional disordered lattice.
- Author
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Slavin, V., Savin, Y., Klimov, M., and Kiyashko, M.
- Subjects
- *
ELECTRON-phonon interactions , *ELECTRONS , *TUNNEL design & construction , *INTEGRALS - Abstract
We have studied the peculiarities of electron transport in one-dimensional disordered chain at the presence of correlations between on-site interaction and tunneling integrals. In the considered models, the disorder in host-lattice sites positions is caused by presence of defects, impurities, existence of electron-phonon interaction, etc. It is shown that for certain combination of parameters the localization of electron state inherited by a various of 1D disordered systems disappears, and electron transport becomes possible. The parameters of this transport are established. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
32. Superconductivity in Alkali Metal-Deposited Monolayer BC: MBC (M = Na, K).
- Author
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Li, Ya-Ping, Yang, Liu, Liu, Hao-Dong, Shang, Shu-Ying, and Chen, Ying-Jie
- Subjects
- *
SUPERCONDUCTING transition temperature , *HIGH temperature superconductors , *ELECTRON-phonon interactions , *ELECTRONIC equipment , *SUPERCONDUCTORS - Abstract
In recent years, as two-dimensional (2D) materials have been widely used in electronic devices, searching for 2D high superconducting transition temperature ( T c ) superconductors has also attracted great attentions. In this work, based on first-principles calculations and Eliashberg equation, the electronic structure, electron-phonon coupling (EPC) and possible superconductivity of alkali metal-deposited monolayer BC: MBC (M = Na, K) are studied. The results show that MBC (M = Na, K) are metallic and potential superconductors. The calculated EPC constants of MBC (M = Na, K) are 0.97 and 1.48, respectively. The strong coupling of MBC (M = Na, K) mainly origins from the coupling between electrons with the in-plane vibration modes of C and B atoms. The T c of MBC (M = Na, K) are 34.1 K and 41.7 K, respectively, and the T c of NaBC can be increased to 45.6 K under 2% biaxial tensile strain, and the T c of KBC can be boosted to 53.8 K under 1% biaxial tensile strain. It is anticipated that the predicted monolayer MBC (M = Na, K) and its strained cases can be realized in future experiments. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
33. Reflections on Zwanzig's theories of dielectric friction.
- Author
-
Bonn, Mischa and Hynes, James T.
- Subjects
- *
CHARGE carrier mobility , *CHEMICAL kinetics , *DIELECTRIC relaxation , *PERMITTIVITY , *ELECTRON-phonon interactions , *SUPERCOOLED liquids - Published
- 2024
- Full Text
- View/download PDF
34. The mechanical compression enhancement of electronic degeneracy in superconducting hydrides.
- Author
-
Hu, Hang, Kiang Ooi, Hsu, and Hu, Anguang
- Subjects
- *
COOPER pair , *ENERGY levels (Quantum mechanics) , *ELECTRON-phonon interactions , *FERMI surfaces , *QUANTUM mechanics - Abstract
As one of the fundamental phenomena in quantum mechanics, quantum degeneracy is a specific regime in which collective and coherent phenomena dominate. The Cooper pair of a metal superconductor is an example of quantum degeneracy. Therefore, it is imperative to understand the dynamic formation and breaking process of quantum degeneracy of high-temperature superconductors relevant to spatial dimension and symmetry constraints. We developed an accurate non-perturbation electron-phonon interaction simulation and applied it to study the dynamic process of removing electronic degeneracy in superconducting hydrides under mechanical compression. The simulation shows that the degenerate electronic energy levels near the Fermi surface may hold more electrons or holes to form Cooper pairs. However, the direct electron-phonon interactions related to specific vibrational motion can remove electronic degeneracy, breaking Cooper pairs even at absolute zero temperature. The specific vibrational motion to stretch chemical bonds can interact with Cooper pairs, spontaneously and dynamically removing all degeneracies. Combined with spatial dimension and symmetry constraints, mechanical compression can enhance the electronic degeneracy to keep Cooper pairs in superconducting hydrides. As a result, such simulations may apply to search for stable high-temperature superconducting hydrides at lower pressures. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
35. A mesoscale modeling framework to predict the microstructural evolution at the scales of laser shock experiments.
- Author
-
Sebastian, Roshan, Chen, Ching, and Dongare, Avinash
- Subjects
- *
ELECTRON-phonon interactions , *SOLID-liquid interfaces , *STRAIN rate , *X-ray diffraction , *TEMPERATURE distribution - Abstract
Short-pulsed lasers enable the investigation of the dynamic response of metals at extreme strain rates of loading. The typical experimental setup to study the dynamic response of metals using lasers uses rear surface velocity profiles to understand the loading stresses generated, and in situ characterization using X-ray diffraction (XRD) enables the real-time investigation of microstructure evolution. However, one of the long-standing challenges in interpreting the experimental results is quantifying the defect/phase fractions or the evolution of hydrodynamic instabilities. As a result, current efforts focus on developing materials modeling methods to predict microstructure evolution during the interaction of lasers and improve the interpretation of experimental diffractograms. This manuscript aims to demonstrate the capability of a newly developed hybrid mesoscale-continuum method to accurately capture the laser energy absorption, the electron-phonon coupling behavior, and the related distribution of temperatures and pressures in the sample at the experimental time and length scales. The capability is developed by combining the mesoscale Quasi-Coarse-Grained (QCGD) method with a continuum two-temperature model (TTM) to model the material response at the length and time scales of in situ laser shock experiments. The QCGD-TTM simulations are able to predict the laser-induced kinetics of melting and the evolution of the solid-liquid interface to quantify the solid/liquid/ablated fractions. The QCGD-TTM simulations are able to correlate the phase fractions with the corresponding rear surface velocity profiles and the temperature and shock pressures generated and can complement the interpretation of results in laser shock experiments. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
36. Spin-phonon coupling in a double-stranded model of DNA.
- Author
-
Peralta, Mayra, Feijoo, Steven, Varela, Solmar, Gutierrez, Rafael, Cuniberti, Gianaurelio, Mujica, Vladimiro, and Medina, Ernesto
- Subjects
- *
ACOUSTIC phonons , *ELECTRON-phonon interactions , *DNA , *CHARGE exchange , *SPIN-orbit interactions , *PHONON scattering - Abstract
We address the electron-spin-phonon coupling in an effective model Hamiltonian for DNA to assess its role in spin transfer involved in the Chiral-Induced Spin Selectivity (CISS) effect. The envelope function approach is used to describe semiclassical electron transfer in a tight-binding model of DNA at half filling in the presence of intrinsic spin–orbit coupling. Spin-phonon coupling arises from the orbital-configuration dependence of the spin–orbit interaction. We find spin-phonon coupling only for the acoustic modes, while the optical modes exhibit electron–phonon interaction without coupling to spin. We derive an effective Hamiltonian whose eigenstates carry spin currents that are protected by spin-inactive stretching optical modes. As optical phonons interact more strongly than acoustic phonons, side buckling and tilting optical base modes will be more strongly associated with decoherence, which allows for the two terminal spin filtering effects found in CISS. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
37. Understanding chiral charge-density wave by frozen chiral phonon.
- Author
-
Zhang, Shuai, Luo, Kaifa, and Zhang, Tiantian
- Subjects
ELECTRON-phonon interactions ,CHARGE density waves ,INELASTIC scattering ,PHONONS ,CHIRALITY - Abstract
Charge density wave (CDW) is discovered within a wide interval in solids, however, its microscopic nature is still not transparent in most realistic materials, and the recently studied chiral ones with chiral structural distortion remain unclear. In this paper, we try to understand the driving forces of chiral CDW transition by chiral phonons from the electron-phonon coupling scenario. We use the prototypal monolayer 1T-TiSe
2 as a case study to unveil the absence of chirality in the CDW transition and propose a general approach, i.e., symmetry-breaking stimuli, to engineer the chirality of CDW in experiments. Inelastic scattering patterns are also studied as a benchmark of chiral CDW (CCDW, which breaks the mirror/inversion symmetry in 2D/3D systems). We notice that the anisotropy changing of Bragg peak profiles, which is contributed by the soft chiral phonons, can show a remarkable signature for CCDW. Our findings pave a path to understanding the CCDW from the chiral phonon perspective, especially in van der Waals materials, and provides a powerful way to manipulate the chirality of CDW. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
38. Complex charge density waves in simple electronic systems of two-dimensional III2–VI3 materials.
- Author
-
Huang, Yu-Ting, Li, Zhen-Ze, Chen, Nian-Ke, Wang, Yeliang, Sun, Hong-Bo, Zhang, Shengbai, and Li, Xian-Bin
- Subjects
CHARGE density waves ,ELECTRON-phonon interactions ,FERMI surfaces ,BRILLOUIN zones ,ELECTRON density - Abstract
Charge density wave (CDW) is the phenomenon of a material that undergoes a spontaneous lattice distortion and modulation of the electron density. Typically, the formation of CDW is attributed to Fermi surface nesting or electron-phonon coupling, where the CDW vector (Q
CDW ) corresponds to localized extreme points of electronic susceptibility or imaginary phonon frequencies. Here, we propose a new family of multiple CDW orders, including chiral Star-of-David configuration in nine 2D III2 –VI3 van der Waals materials, backed by first-principles calculations. The distinct feature of this system is the presence of large and flat imaginary frequencies in the optical phonon branch across the Brillouin zone, which facilitates the formation of the diverse CDW phases. The electronic structures of 2D III2 –VI3 materials are relatively simple, with only III-s,p and VI-p orbitals contributing to the formation of the CDW order. Despite that, the CDW transitions involve both metal-to-insulator and insulator-to-insulator transitions, accompanied by a significant increase in the bandgap caused by an enhanced electronic localization. Our study not only reveals a new dimension in the family of 2D CDWs, but is also expected to offer deeper insights into the origins of the CDWs. This study introduces a family of multiple charge-density-wave orders in 2D III2 –VI3 materials, including the chiral Star-of-David configuration. The charge-density-wave transitions involve both metal-to-insulator and insulator-to-insulator transitions, providing a platform for understanding the origins of charge density waves. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
39. Screening the organic materials database for superconducting metal-organic frameworks.
- Author
-
Tyner, Alexander and Balatsky, Alexander V.
- Subjects
- *
ELECTRON-phonon interactions , *SUPERCONDUCTORS , *HIGH throughput screening (Drug development) , *UNIT cell , *METAL-organic frameworks - Abstract
The increasing financial and environmental cost of many inorganic materials has motivated study into organic and "green" alternatives. However, most organic compounds contain a large number of atoms in the primitive unit cell, posing a significant barrier to high-throughput screening for functional properties. In this work, we attempt to overcome this challenge and identify superconducting candidates among the metal-organic-frameworks in the organic materials database using a recently proposed proxy for the electron-phonon coupling. We then isolate the most promising candidate for in-depth analysis, C9H8Mn2O11, providing evidence for superconductivity below 100mK. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
40. Discovery of superconductivity and electron-phonon drag in the non-centrosymmetric Weyl semimetal LaRhGe3.
- Author
-
Oudah, Mohamed, Kung, Hsiang-Hsi, Sahu, Samikshya, Heinsdorf, Niclas, Schulz, Armin, Philippi, Kai, De Toro Sanchez, Marta-Villa, Cai, Yipeng, Kojima, Kenji, Schnyder, Andreas P., Takagi, Hidenori, Keimer, Bernhard, Bonn, Doug A., and Hallas, Alannah M. more...
- Subjects
MUON spin rotation ,ELECTRON-phonon interactions ,THERMAL conductivity measurement ,ELECTRICAL resistivity ,SPECIFIC heat - Abstract
We present an exploration of the effect of electron-phonon coupling and broken inversion symmetry on the electronic and thermal properties of the semimetal LaRhGe
3 . Our transport measurements reveal evidence for electron-hole compensation at low temperatures, resulting in a large magnetoresistance of 3000% at 1.8 K and 14 T. The carrier concentration is on the order of 1021 /cm3 with high carrier mobilities of 2000 cm2 /Vs. When coupled to our theoretical demonstration of symmetry-protected almost movable Weyl nodal lines, we conclude that LaRhGe3 supports a Weyl semimetallic state. We discover superconductivity in this compound with a Tc of 0.39(1) K and Bc (0) of 2.2(1) mT, with evidence from specific heat and transverse-field muon spin relaxation. We find an exponential dependence in the normal state electrical resistivity below ~50 K, while Seebeck coefficient and thermal conductivity measurements each reveal a prominent peak at low temperatures, indicative of strong electron-phonon interactions. To this end, we examine the temperature-dependent Raman spectra of LaRhGe3 and find that the lifetime of the lowest energy A1 phonon is dominated by phonon-electron scattering instead of anharmonic decay. We conclude that LaRhGe3 has strong electron-phonon coupling in the normal state, while the superconductivity emerges from weak electron-phonon coupling. These results open up the investigation of electron-phonon interactions in the normal state of superconducting non-centrosymmetric Weyl semimetals. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
41. Synthesis and structure of a non-van-der-Waals two-dimensional coordination polymer with superconductivity.
- Author
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Pan, Zhichao, Huang, Xing, Fan, Yunlong, Wang, Shaoze, Liu, Yiyu, Cong, Xuzhong, Zhang, Tingsong, Qi, Shichao, Xing, Ying, Zheng, Yu-Qing, Li, Jian, Zhang, Xiaoming, Xu, Wei, Sun, Lei, Wang, Jian, and Dou, Jin-Hu more...
- Subjects
COORDINATION polymers ,ELECTRON-phonon interactions ,ELECTRON-electron interactions ,CONJUGATED polymers ,SINGLE crystals - Abstract
Two-dimensional conjugated coordination polymers exhibit remarkable charge transport properties, with copper-based benzenehexathiol (Cu-BHT) being a rare superconductor. However, the atomic structure of Cu-BHT has remained unresolved, hindering a deeper understanding of the superconductivity in such materials. Here, we show the synthesis of single crystals of Cu
3 BHT with high crystallinity, revealing a quasi-two-dimensional kagome structure with non-van der Waals interlayer Cu-S covalent bonds. These crystals exhibit intrinsic metallic behavior, with conductivity reaching 103 S/cm at 300 K and 104 S/cm at 2 K. Notably, superconductivity in Cu3 BHT crystals is observed at 0.25 K, attributed to enhanced electron-electron interactions and electron-phonon coupling in the non-van der Waals structure. The discovery of this clear correlation between atomic-level crystal structure and electrical properties provides a crucial foundation for advancing superconductor coordination polymers, with potential to revolutionize future quantum devices. Two-dimensional conjugated coordination polymers can show large electrical conductivity. Here, the authors synthesize high-quality single crystals of Cu3 BHT to unveil the atomic structure and intrinsic superconducting properties. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
42. Observation of interlayer plasmon polaron in graphene/WS2 heterostructures.
- Author
-
Ulstrup, Søren, in 't Veld, Yann, Miwa, Jill A., Jones, Alfred J. H., McCreary, Kathleen M., Robinson, Jeremy T., Jonker, Berend T., Singh, Simranjeet, Koch, Roland J., Rotenberg, Eli, Bostwick, Aaron, Jozwiak, Chris, Rösner, Malte, and Katoch, Jyoti more...
- Subjects
ELECTRONIC excitation ,CONDUCTION electrons ,PHOTOELECTRON spectroscopy ,CONDUCTION bands ,ELECTRON-phonon interactions - Abstract
Harnessing electronic excitations involving coherent coupling to bosonic modes is essential for the design and control of emergent phenomena in quantum materials. In situations where charge carriers induce a lattice distortion due to the electron-phonon interaction, the conducting states get "dressed", which leads to the formation of polaronic quasiparticles. The exploration of polaronic effects on low-energy excitations is in its infancy in two-dimensional materials. Here, we present the discovery of an interlayer plasmon polaron in heterostructures composed of graphene on top of single-layer WS
2 . By using micro-focused angle-resolved photoemission spectroscopy during in situ doping of the top graphene layer, we observe a strong quasiparticle peak accompanied by several carrier density-dependent shake-off replicas around the single-layer WS2 conduction band minimum. Our results are explained by an effective many-body model in terms of a coupling between single-layer WS2 conduction electrons and an interlayer plasmon mode. It is important to take into account the presence of such interlayer collective modes, as they have profound consequences for the electronic and optical properties of heterostructures that are routinely explored in many device architectures involving 2D transition metal dichalcogenides. Here, the authors report the observation of an interlayer plasmon polaron in heterostructures composed of graphene and monolayer WS2 . This is manifested in the ARPES spectra as a strong quasiparticle peak accompanied by several carrier density-dependent shake-off replicas around the WS2 conduction band minimum. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
43. Evaluating size effects on the thermal conductivity and electron-phonon scattering rates of copper thin films for experimental validation of Matthiessen's rule.
- Author
-
Islam, Md. Rafiqul, Karna, Pravin, Tomko, John A., Hoglund, Eric R., Hirt, Daniel M., Hoque, Md Shafkat Bin, Zare, Saman, Aryana, Kiumars, Pfeifer, Thomas W., Jezewski, Christopher, Giri, Ashutosh, Landon, Colin D., King, Sean W., and Hopkins, Patrick E. more...
- Subjects
ELECTRON scattering ,THIN films ,ELECTRON transport ,ELECTRON-phonon interactions ,COPPER films ,PHONON scattering ,THERMAL conductivity - Abstract
As metallic nanostructures shrink towards the size of the electronic mean free path, thermal conductivity decreases due to increased electronic scattering rates. Matthiessen's rule is commonly applied to assess changes in electron scattering rates, although this rule has not been validated experimentally at typical operating temperatures for most of the electronic systems (e.g., near room temperature). In this study, we experimentally evaluate the validity of Matthiessen's rule in determining the thermal conductivity of thin metal films by measuring the in-plane thermal conductivity and electronic scattering rates of copper (Cu) films with varying thicknesses (27 nm — 5 µm), microstructures, and grain boundary segregation. Comparing total electron scattering rates measured with infrared ellipsometry to infrared ultrafast pump-probe measurements, we find that the electron-phonon coupling factor is independent of film thickness, whereas the total electronic scattering rate increases with decreasing film thickness. Our findings provide experimental validation of Matthiessen's rule for electron transport in thin metal films at room temperature and also introduce an approach to discern critical heat transfer processes in thin metal interconnects, which holds significance for the advancement of future CMOS technology. The authors examine Matthiessen's rule for determining the thermal conductivity in thin Cu film. They attribute reductions in the thermal conductivity of Cu to electron scattering at boundaries and grain boundary segregation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
44. Phonon Drag Contribution to Thermopower for a Heated Metal Nanoisland on a Semiconductor Substrate.
- Author
-
Arkhipov, Alexander, Trofimovich, Karina, Arkhipov, Nikolay, and Gabdullin, Pavel
- Subjects
- *
ELECTRIC charge , *ELECTRON-phonon interactions , *ELECTRON emission , *DRAG (Aerodynamics) , *EQUATIONS of motion - Abstract
The possible contribution of phonon drag effect to the thermoelectrically sustained potential of a heated nanoisland on a semiconductor surface was estimated in a first principal consideration. We regarded electrons and phonons as interacting particles, and the interaction cross-section was derived from the basic theory of semiconductors. The solution of the equation of motion for average electrons under the simultaneous action of phonon drag and electric field gave the distributions of phonon flux, density of charge carriers and electric potential. Dimensional suppression of thermal conductance and electron-phonon interaction were accounted for but found to be less effective than expected. The developed model predicts the formation of a layer with a high density of charge carriers that is practically independent of the concentration of dopant ions. This layer can effectively intercept the phonon flow propagating from the heated nanoisland. The resulting thermoEMF can have sufficient magnitudes to explain the low-voltage electron emission capability of nanoisland films of metals and sp2-bonded carbon, previously studied by our group. The phenomenon predicted by the model can be used in thermoelectric converters with untypical parameters or in systems for local cooling. [ABSTRACT FROM AUTHOR] more...
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- 2024
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45. Absence of electron-phonon coupling superconductivity in the bilayer phase of La3Ni2O7 under pressure.
- Author
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Ouyang, Zhenfeng, Gao, Miao, and Lu, Zhong-Yi
- Subjects
ELECTRON-phonon interactions ,HIGH temperature superconductors ,CHARGE density waves ,FERMI surfaces ,DENSITY functional theory ,SUPERCONDUCTING transition temperature - Abstract
An experimental study found superconductivity in bilayer phase of La
3 Ni2 O7 , with the highest superconducting transition temperature (Tc ) ∼ 80 K under pressure. Recently, some reports claimed that there exists a competitive monolayer-trilayer structural phase in La3 Ni2 O7 compounds. We perform the first-principles calculations and find that bilayer phase of La3 Ni2 O7 is energetically favorable under pressure. Although extensive studies have been done to investigate the electronic correlation and potential superconducting pairing mechanism in bilayer phase of La3 Ni2 O7 , the phonon properties and electron-phonon coupling (EPC) in the high-pressure I4/mmm phase of La3 Ni2 O7 are not reported. Using the density functional theory (DFT) combined with Wannier interpolation technique, we study the phonon properties and EPC in bilayer phase of La3 Ni2 O7 under 29.5 GPa. Our findings reveal that EPC is insufficient to explain the observed superconducting Tc ∼ 80 K. And the calculated Fermi surface nesting may explain the experimentally observed charge density wave (CDW) transition in bilayer phase of La3 Ni2 O7 . Our calculations substantiate that bilayer phase of La3 Ni2 O7 is an unconventional superconductor. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
46. Enhanced cation ordering, electron-spin-phonon interactions and Fano resonance in half-metallic Sr2FeMoO6 thin films.
- Author
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Yadav, Ekta, Sahoo, Jayaprakash, and Mavani, Krushna R
- Subjects
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THIN films , *ELECTRON-phonon interactions , *PULSED laser deposition , *CURIE temperature , *HEUSLER alloys , *RAMAN spectroscopy , *RAMAN scattering , *FANO resonance , *OXYGEN - Abstract
We report the presence of electron-spin-phonon interactions in half-metallic ferromagnetic Sr2FeMoO6 (SFMO) double perovskite thin films using temperature-dependent Raman spectroscopy. A series of SFMO thin films have been prepared on LaAlO3 (001) single-crystal substrate using the Pulsed Laser Deposition technique. These depositions have been made in different gas-conditions such as in vacuum, and under nitrogen and oxygen gas pressures. At room temperature, Raman spectra manifest a Fano feature which indicates the presence of electron-phonon coupling in the films. The electron-phonon coupling strength further changes with a change in deposition conditions. Magnetization results show that the SFMO film grown in vacuum has the highest saturation magnetization which suggests better cation ordering as compared to the other films. For enhanced understanding, Raman spectra were recorded at varied temperatures and the data were analyzed by theoretical model fittings. A parameter quantifying temperature-dependent anharmonic nature of phonons has been derived using Balkanski model fits. This parameter shows a drastic deviation in the vicinity of Curie temperatures, manifesting a spin-phonon coupling in SFMO films. We further show that the spin-phonon coupling strengthens with improved Fe–Mo ordering. Any experimental observation of spin-phonon coupling has not been reported for SFMO systems till date. The magnetization data corroborate well with these observations made by Raman measurements. Our results of Raman spectroscopy, magnetization and resistivity collectively suggest that the SFMO films exhibit electron-spin-phonon interactions, which are influenced by the cation ordering. We also devised out the method of relating the anharmonic nature of Raman modes with the degree of Fe–Mo ordering and spin-phonon coupling in double-perovskite materials. [ABSTRACT FROM AUTHOR] more...
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- 2024
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47. Temperature-dependent electron–phonon coupling changes the damage cascades in neutron-irradiation molecular dynamics simulation in W.
- Author
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Shin, Younggak, Kang, Keonwook, and Lee, Byeongchan
- Subjects
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ELECTRON-phonon interactions , *MOLECULAR dynamics , *NEUTRON irradiation , *THERMAL conductivity , *ELECTRON temperature , *COOLDOWN - Abstract
We present a first-principles-based electron-temperature model that can be used in atomistic calculations. The electron–phonon coupling coefficient in the model is derived from the density of states as a function of electron temperature, and the thermal conductivity of tungsten from our model shows significant improvement over the baseline atomistic calculations in which only ion-thermal contribution to the thermal conductivity is available. The correction to the thermal conductivity also changes damage cascades as cascades cool down more rapidly within our model. The mobility of defects is consequently reduced, leaving more residual damage than the predictions without an electron-temperature model. [ABSTRACT FROM AUTHOR] more...
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- 2024
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48. Self-trapped emissions in 2D lead-free halide perovskites driven by divalent spacer cations.
- Author
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Freitas, Andre L. M., Tofanello, Aryane, Caturello, Naidel A. M. S., Barbosa, Karla K. F., and Ferreira, Fabio F.
- Subjects
- *
ELECTRON-phonon interactions , *STRUCTURAL stability , *CATIONS , *HALIDES , *PEROVSKITE , *EXCITON theory - Abstract
The mono- and divalent spacer cation investigation in sodium/indium-based 2D double perovskites revealed significant impacts on optoelectronic properties due to distortions in the inorganic layers. The strong electron–phonon coupling in a novel lead-free Dion–Jacobson phase highlights a promising class for broad-emission devices based on self-trapped excitons (STE), offering enhanced structural stability. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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49. Analysis of structural disorder on Raman spectra of semiconductors.
- Author
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Rambadey, Omkar V., Gupta, Minal, Kumar, Anil, and Sagdeo, Pankaj R.
- Subjects
- *
LATTICE dynamics , *ELECTRON-phonon interactions , *SEMICONDUCTORS , *PHONONS , *PHASE transitions - Abstract
This Tutorial provides a fundamental discussion on the lattice dynamics of physical systems introduced with disorder and, hence, the importance of Raman spectroscopy (RS) technique to probe these impacts. The article first discusses, analytically, the impact of disorder on the symmetry allowed phonon modes of the system by considering the finite probability of discrete-continuum interference in terms of electron–phonon interactions in the system, thereby briefly discussing the relevant experimental reports, followed by providing an ephemeral description on the loss of translational symmetry in the lattice environment under the strain field generated due to disorder and its consequence as relaxation of the q → = 0 selection rule in terms of RS; thus, correlating these discussions with the observation of the symmetry-forbidden disorder induced phonon modes. The same is also elaborated with the experimental reports on various systems of ABO3 and AO2 kinds, where A and B are cations that exhibit the occurrence of disorder induced phonon modes in the respective Raman spectra because of the disorder introduced into the host lattice, and which is emphasized to be not originating due to any structural phase transitions. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
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50. Fundamentals and applications of piezotronics for catalysis: Fundamentals and applications
- Author
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Wang, Xudong, Wu, Jyh Ming, and Li, Linlin
- Published
- 2025
- Full Text
- View/download PDF
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