2,970 results on '"SPIN polarization"'
Search Results
2. Study of Spin-Polarization Effects of Collective Excitations in Double-Layer GrapheneStructures
- Author
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Phuong, Dong Thi Kim and Van Men, Nguyen
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- 2024
- Full Text
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3. Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices.
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Suto, Hirofumi, Barwal, Vineet, Simalaotao, Kodchakorn, Li, Zehao, Masuda, Keisuke, Sasaki, Taisuke, Miura, Yoshio, and Sakuraba, Yuya
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SPIN polarization , *GIANT magnetoresistance , *HEUSLER alloys , *THIN films , *MAGNETIC materials , *FERROELECTRIC thin films - Abstract
Magnetic materials with high negative spin polarization have been sought as a building block to increase the design freedom and performance of spintronics devices. In this paper, we investigate negative spin polarization of Mn2VGa Heusler alloy in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. We fabricated an epitaxial CPP-GMR stack consisting of Mn2VGa/Ag/CoFe with L21 ordering in the Mn2VGa layer and observed negative magnetoresistance (MR), which provided evidence of negative spin polarization. The MR ratio depended on thermal treatments (deposition at an elevated temperature and post-annealing), because these processes affected the ordering, roughness, and magnetic properties of Mn2VGa. The maximum MR ratio reached −1.8% at room temperature and −3.0% at low temperatures, representing the highest among the negative MR values in pseudo-spin-valve CPP-GMR devices despite the underestimation due to an incomplete antiparallel magnetization configuration. These findings demonstrate the potential of Mn2VGa for a material with high negative spin polarization. [ABSTRACT FROM AUTHOR]
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- 2024
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4. Collisional corrections to spin polarization from quantum kinetic theory using Chapman-Enskog expansion
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Fang, Shuo and Pu, Shi
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High Energy Physics - Phenomenology ,High Energy Physics - Theory ,Nuclear Theory - Abstract
We have investigated the collisional corrections to the spin polarization pseudo-vector, $\delta\mathcal{P}^{\mu}$, using quantum kinetic theory in Chapman-Enskog expansion. We derive the spin Boltzmann equation incorporating M{\o}ller scattering process. We further consider two distinct scenarios using hard thermal loop approximations for simplification. In scenario (I), the vector charge distribution function is treated as off-equilibrium under the validity domain of gradient expansion. Remarkably, the polarization induced by gradients of thermal chemical potential and shear viscous tensors are modified, but $\delta\mathcal{P}_{\textrm{ }}^{\mu}$ in this scenario does not depend on the coupling constant. In scenario (II), the vector charge distribution function is assumed to be in local thermal equilibrium. Then collisional corrections $\delta\mathcal{P}_{\textrm{ }}^{\mu}$ in this scenario are at $\mathcal{O}(\hbar^{2}\partial^{2})$. Additionally, we evaluate the $\delta\mathcal{P}^{\mu}$ using relaxation time approach for comparative analysis. Our results establish the theoretical framework necessary for the future numerical investigations on the interaction corrections to spin polarization., Comment: 32 pages, 1 figure
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- 2024
5. Nuclear spin polarization in silicon carbide at room temperature in the Earth's magnetic field
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Anisimov, A. N., Poshakinskiy, A. V., and Astakhov, G. V.
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Condensed Matter - Materials Science - Abstract
Coupled electron-nuclear spins represent a promising quantum system, where the optically induced electron spin polarization can be dynamically transferred to nuclear spins via the hyperfine interaction. Most experiments on dynamic nuclear polarization (DNP) are performed at cryogenic temperatures and/or in moderate external magnetic fields, the latter approach being very sensitive to the magnetic field orientation. Here, we demonstrate that the $^{29}$Si nuclear spins in SiC can be efficiently polarized at room temperature even in the Earth's magnetic field. We exploit the asymmetric splitting of the optically detected magnetic resonance (ODMR) lines inherent to half-integer $S = 3/2$ electron spins, such that the certain transitions involving $^{29}$Si nuclei can be clearly separated and selectively addressed using radiofrequency (RF) fields. As a model system, we use the V3 silicon vacancy in 6H-SiC, which has the zero-filed splitting parameter comparable with the hyperfine interaction constant. Our theoretical model considers DNP under optical excitation in combination with RF driving and agrees very well with the experimental data. In the case of high-fidelity electron spin polarization, the proposed DNP protocol leads to ultra-deep optical cooling of nuclear spins with an effective temperature of about 50 nK. These results provide a straightforward approach for controlling the nuclear spin under ambient conditions, representing an important step toward realizing nuclear hyperpolarization for magnetic resonance imaging and long nuclear spin memory for quantum logic gates., Comment: 9 pages, 4 figures
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- 2024
6. All optical excitation of spin polarization in d-wave altermagnets
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Weber, Marius, Wust, Stephan, Haag, Luca, Akashdeep, Akashdeep, Leckron, Kai, Schmitt, Christin, Ramos, Rafael, Kikkawa, Takashi, Saitoh, Eiji, Kläui, Mathias, Šmejkal, Libor, Sinova, Jairo, Aeschlimann, Martin, Jakob, Gerhard, Stadtmüller, Benjamin, and Schneider, Hans Christian
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The recently discovered altermagnets exhibit collinear magnetic order with zero net magnetization but with unconventional spin-polarized d/g/i-wave band structures, expanding the known paradigms of ferromagnets and antiferromagnets. In addition to novel current-driven electronic transport effects, the unconventional time-reversal symmetry breaking in these systems also makes it possible to obtain a spin response to linearly polarized fields in the optical frequency domain. We show through ab-initio calculations of the prototypical d-wave altermagnet RuO$_2$, with $[C_2\|C_{4z}]$ symmetry combining twofold spin rotation with fourfold lattice rotation, that there is an optical analogue of a spin splitter effect, as the coupling to a linearly polarized exciting laser field makes the d-wave character of the altermagnet directly visible. By magneto-optical measurements on RuO$_2$ films of a few nanometer thickness, we demonstrate the predicted connection between the polarization of an ultrashort pump pulse and the sign and magnitude of a persistent optically excited electronic spin polarization. Our results point to the possibility of exciting and controlling the electronic spin polarization in altermagnets by such ultrashort optical pulses. In addition, the possibility of exciting an electronic spin polarization by linearly polarized optical fields in a compensated system is a unique consequence of the altermagnetic material properties, and our experimental results therefore present an indication for the existence of an altermagnetic phase in ultrathin RuO$_2$ films.
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- 2024
7. Chirality-dependent spin polarization in diffusive metals: linear and quadratic responses
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Kato, Yusuke, Suzuki, Yuta, Sato, Takuro, Yamamoto, Hiroshi M., Togawa, Yoshihiko, Kusunose, Hiroaki, and Kishine, Jun-ichiro
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
We study spin polarization induced by electric fields in an isotropic chiral metal with boundaries using the Boltzmann formalism. We calculate both spin polarization in bulk in the linear response and antiparallel spin polarization near the boundary in the quadratic response against electric fields. We also work out spin polarization induced by the fluctuating electric fields, i.e., noises. Based on these results, we address chirality-induced spin selectivity (CISS) without biased inputs, CISS at room temperature, and the enantio-selective interaction between chiral materials and a magnetic substrate., Comment: 6 pages, 3 figures, +Supplemental Material(2pages)
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- 2024
8. Spin polarization of $\Lambda$ hyperons along beam direction in p+Pb collisions at $\sqrt{s_{NN}}=8.16$ TeV using hydrodynamic approaches
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Yi, Cong, Wu, Xiang-Yu, Zhu, Jie, Pu, Shi, and Qin, Guang-You
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High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
We have implemented the 3+1 dimensional CLVisc hydrodynamics model with TRENTO-3D initial conditions to investigate the spin polarization of $\Lambda$ hyperons along the beam direction in p+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV. Following our previous theoretical framework based on quantum kinetic theory, we consider three different scenarios: $\Lambda$ equilibrium, $s$ quark equilibrium, and iso-thermal equilibrium scenarios. We have computed the second Fourier sine coefficients of spin polarization along the beam direction, denoted as $\left\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \right\rangle$, with $\phi_{p} - \Psi_{2}$ being the azimuthal angle relative to the second-order event plane $\Psi_{2}$, as functions of multiplicity, transverse momentum and pseudo-rapidity in the three scenarios. Additionally, we have also computed the spin polarization along the beam direction, $P_{z}$, as a function of the azimuthal angle. We find that the spin polarization induced by thermal vorticity always provides an opposite contribution compared to the shear-induced polarization in p+Pb collisions. The total spin polarization computed by the current hydrodynamic model disagrees with the data measured by LHC-CMS experiments. Our findings imply that other non-flow effects may play a crucial role in p+Pb collisions., Comment: 8 pages, 5 figures and 1 table. A new figure for local polarization as a function of pseudo-rapidity is added. submitted to PRC
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- 2024
9. Spin polarization of fermions at local equilibrium: Second-order gradient expansion
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Sheng, Xin-Li, Becattini, Francesco, Huang, Xu-Guang, and Zhang, Zhong-Hua
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High Energy Physics - Theory ,High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
We present a calculation of the spin polarization of spin-1/2 fermions in a relativistic fluid at local thermodynamic equilibrium at the second order in the gradient expansion, including second-order derivatives. The second-order derivative terms vanish if the local equilibrium hypersurface is the hyperplane $t=const$ in the collision center-of-mass frame. However, since the freeze-out hypersurface has a non-trivial space-time structure, these terms may result in a non-vanishing contribution to the spin polarization, whose magnitude needs to be assessed with numerical computations., Comment: 18 pages, 2 figures
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- 2024
10. Spin Splitting in Altermagnetic RuO$_2$ Enables Field-free Spin-Orbit Torque Switching via Dominant Out-of-Plane Spin Polarization
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Li, Zhuoyi, Zhang, Zhe, Lu, Xianyang, and Xu, Yongbing
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Physics - Applied Physics - Abstract
Researchers have recently identified a novel class of magnetism, termed "altermagnetism", which exhibits characteristics of both ferromagnetism and antiferromagnetism. Here, we report a groundbreaking discovery of efficient field-free spin-orbit torque (SOT) switching in a RuO$_2$ (101)/Co/Pt/Co/Pt/Ta structure. Our results demonstrate that the spin current flows along the [100] axis, induced by the in-plane charge current, with the spin polarization direction aligned parallel to the N\'eel vector. These z-polarized spins generate an out-of-plane anti-damping torque, enabling deterministic switching of the Co/Pt layer without the necessity of an external magnetic field. The altermagnetic spin splitting effect (ASSE) in RuO$_2$ promotes the generation of spin currents with pronounced anisotropic behavior, maximized when the charge current flows along the [010] direction. This unique capability yields the highest field-free switching ratio, maintaining stable SOT switching within an external field range of approximately 400 Oe. Notably, ASSE dominates the spin current, especially when the current is aligned with the [010] direction ({\theta} = 90{\deg}). Here, the spin polarization component creates a substantial field-like effective field, surpassing the damping-like field from . This highlights the crucial role of in enhancing spin-torque efficiency and elucidating spin flow modulation mechanics in this crystalline context. Our study highlights the potential of RuO$_2$ as a powerful spin current generator, paving the way for practical applications in spin-torque switching technologies and other cutting-edge spintronic devices.
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- 2024
11. Room-temperature optical spin polarization of an electron spin qudit in a vanadyl -- free base porphyrin dimer
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Privitera, Alberto, Chiesa, Alessandro, Santanni, Fabio, Carella, Angelo, Ranieri, Davide, Caneschi, Andrea, Krzyaniak, Matthew D., Young, Ryan M., Wasielewski, Michael R., Carretta, Stefano, and Sessoli, Roberta
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Quantum Physics ,Physics - Chemical Physics - Abstract
Photoexcited organic chromophores appended to molecular qubits can serve as a source of spin initialization or multi-level qudit generation for quantum information applications. So far, this approach has been primarily investigated in chromophore/stable radical systems. Here, we extend this concept to a meso-meso linked oxovanadium(IV) porphyrin - free base porphyrin dimer. Femtosecond transient absorption experiments reveal that photoexcitation of the free base porphyrin leads to picosecond triplet state formation via enhanced intersystem crossing. Time-resolved electron paramagnetic resonance (TREPR) experiments carried out at both 85 K and room temperature reveal the formation of a long-lived spin-polarized quartet state through triplet-doublet spin mixing. Notably, a distinct hyperfine structure arising from the interaction between the electron spin quartet state and the vanadyl nucleus (51V, I=7/2) is evident, with the quartet state exhibiting long-lived spin polarization even at room temperature. Theoretical simulations of the TREPR spectra confirm the photogenerated quartet state and provide insights into the non-Boltzmann spin populations. Exploit-ing this phenomenon affords the possibility of using photoinduced triplet states in porphyrins for quantum information as a resource to polarize and magnetically couple molecular electronic or nuclear spin qubits and qudits.
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- 2024
12. Investigating the hyperfine systematic error and relative phase in low spin-polarization alkali FID magnetometers
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Hewatt, D. P., Ellmeier, M., Kiehl, C., Menon, T. S., Pollock, J. W., Regal, C. A., and Knappe, S.
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Physics - Atomic Physics - Abstract
Alkali-metal optically-pumped magnetometers are prone to inaccuracies arising from the overlap of the average F = I + 1/2 and F = I - 1/2 ground-state Zeeman resonances. We employ density-matrix simulations and experiments to investigate how this hyperfine systematic error varies with spin polarization in a $^{87}$Rb free-induction-decay (FID) magnetometer. At low spin polarizations, ($P \leq 0.5$), this effect causes single-frequency magnetic-field extraction techniques to exhibit inaccuracies up to approximately 3.5 nT. Density-matrix simulations reveal that this bias can be traced to the relative amplitude and phase between the F = I $\pm$ 1/2 hyperfine ground-state manifolds in the FID spin precession signal. We show that this systematic error can be mitigated using either a double-frequency fitting model that accounts for the relative amplitude and phase or synchronous-pulse pumping, that minimizes the F = 1 contribution to the FID signal. Theoretical simulations predict accuracies within 0.5 nT for both techniques across a wide range of spin polarizations, suggesting a sevenfold enhancement over single-frequency extraction methods. Our experiments validate this, showcasing a variation in the extracted field below 1 nT, a 3.5-fold improvement compared to single-frequency extraction methods. Furthermore, the mitigation techniques demonstrate agreement of the extracted magnetic field within 1.5 nT., Comment: 13 pages, 8 figures
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- 2024
13. The electromagnetic form factors and spin polarization of $\Lambda_c^+$ in the process $e^+ e^- \to \Lambda^+_c \bar{\Lambda}^-_c$
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Chen, Cheng, Yan, Bing, and Xie, Ju-Jun
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High Energy Physics - Phenomenology - Abstract
The total cross sections of the process $e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^-$ close to the threshold are calculated within the vector meson dominance model. It is found that the theoretical results can describe the current experimental measurements. In particular, the results for the angular distribution parameters about the differential cross section are consistent with the experiments from BESIII Collaboration. In addition, the relative phase $\Delta \Phi$ of the electromagnetic form factors was given, and the spin polarization of $\Lambda_c^+$ is predicted at center-mass energy $4.7 \ \rm GeV$. It is hopeful to provide a new perspective on the characteristics of the charmed baryon $\Lambda_c^+$., Comment: 6 pages,6 figures
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- 2024
14. Probing the spin polarization of an Anderson impurity
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Bagchi, Mahasweta, Tounsi, Tfyeche Y., Safeer, Affan, van Efferen, Camiel, Rosch, Achim, Michely, Thomas, Jolie, Wouter, Costi, Theo A., and Fischer, Jeison
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
We report spin-polarized scanning tunneling microscopy measurements of an Anderson impurity system in MoS$_{2}$ mirror twin boundaries, where both the quantum confined impurity state and the Kondo resonance resulting from the interaction with the substrate are accessible. Using a spin-polarized tip, we observe magnetic field induced changes in the peak heights of the Anderson impurity states as well as in the magnetic field-split Kondo resonance. Quantitative comparison with numerical renormalization group calculations provides evidence of the notable spin polarization of the spin-resolved impurity spectral function under the influence of a magnetic field. Moreover, we extract the field and temperature dependence of the impurity magnetization from the differential conductance measurements and demonstrate that this exhibits the universality and asymptotic freedom of the $S=1/2$ Kondo effect. This work shows that mirror twin boundaries can be used as a testing ground for theoretical predictions on quantum impurity models.
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- 2024
15. Electric toroidal dipole order and hidden spin polarization in ferroaxial materials
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Bhowal, Sayantika and Spaldin, Nicola A.
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Condensed Matter - Materials Science - Abstract
We investigate the role of electric toroidal dipoles in the prototypical ferroaxial materials NiTiO$_3$ and K$_2$Zr(PO$_4$)$_2$, which undergo ferroaxial structural phase transitions of order-disorder and displacive type, respectively. Using first-principles electronic structure theory, we compute the evolution across the ferroaxial transitions of the local electric toroidal dipole moments, defined both in terms of the vortices formed by local dipoles, as well as as the cross product of orbital and spin angular momenta. Our calculations confirm that the electric toroidal dipole acts as the order parameter for these ferroaxial transitions and highlight the importance of spin-orbit coupling in generating a non-zero atomic-site electric toroidal dipole moment. We find that, while the ferroaxial phases of NiTiO$_3$ and K$_2$Zr(PO$_4$)$_2$ preserve global inversion symmetry, they contain inversion-symmetry-broken sub-units that generate vortices of local electric dipole moments. In addition to causing the net electric toroidal dipole moment, these vortices induce a hidden spin polarization in the band structure., Comment: 8 pages, 7 figures
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- 2024
16. Symmetry-controlled SrRuO3/SrTiO3/SrRuO3 magnetic tunnel junctions:Spin polarization and its relevance to tunneling magnetoresistance
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Samanta, Kartik and Tsymbal, Evgeny Y.
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Magnetic tunnel junctions (MTJs), that consist of two ferromagnetic electrodes separated by an insulating barrier layer, have non-trivial fundamental properties associated with spin-dependent tunneling. Especially interesting are fully crystalline MTJs where spin-dependent tunneling is controlled by the symmetry group of wave vector. In this work, using first-principles quantum-transport calculations, we explore spin-dependent tunneling in fully crystalline SrRuO3/SrTiO3/SrRuO3 (001) MTJs and predict tunneling magnetoresistance (TMR) of nearly 3000%. We demonstrate that this giant TMR effect is driven by symmetry matching (mismatching) of the incoming and outcoming Bloch states in the SrRuO3 (001) electrodes and evanescent states in the SrTiO3 (001) barrier. We argue that under the conditions of symmetry-controlled transport, spin polarization, whatever definition is used, is not a relevant measure of spin-dependent tunneling. In the presence of diffuse scattering, however, e.g. due to localized states in the band gap of the tunnel barrier, symmetry matching is no longer valid and TMR in SrRuO3/SrTiO3/SrRuO3 (001) MTJs is strongly reduced. Under these conditions, the spin polarization of the interface transmission function becomes a valid measure of TMR. These results provide an important insight into understanding and optimizing TMR in all-oxide MTJs., Comment: 10 pages, 6 figures
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- 2024
17. Spin polarization in heavy-ion collisions induced by thermal vorticity and thermal shear
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Buzzegoli, M.
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Nuclear Theory - Abstract
The vorticity is a quantity defined in a relativistic fluid that describes how much a fluid element is rotating and accelerating. By measuring the spin polarization of hadrons, it was found that the quark gluon plasma produced in heavy-ion collisions is the most "vorticous" fluid ever observed. More generally, this opens the possibility to study the physics of QCD matter using spin. Here I use statistical quantum field theory applied to a fluid in local thermodynamic equilibrium to show how to connect the average spin of a fermion with hydrodynamic quantities, and in particular with the thermal vorticity and the thermal shear. I show that the spin polarization of a Dirac particle induced by thermal vorticity is related to the gravitational (in medium) form factor related to spin-rotation coupling. For these reasons, as we are understanding the role of spin in hydrodynamics and in heavy-ion collisions, spin is becoming a promising tool to investigate the properties of QCD and whose applications are just begun to be explored., Comment: 9 pages, SPIN2023 conference proceedings
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- 2024
18. Longitudinal spin polarization in a thermal model with dissipative corrections
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Banerjee, Soham, Bhadury, Samapan, Florkowski, Wojciech, Jaiswal, Amaresh, and Ryblewski, Radoslaw
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High Energy Physics - Phenomenology ,High Energy Physics - Theory ,Nuclear Theory - Abstract
In this work, we address the problem of longitudinal spin polarization of the $\Lambda$ hyperons produced in relativistic heavy-ion collisions. We combine a relativistic kinetic-theory framework that includes spin degrees of freedom treated in a classical way with the freeze-out parametrization used in previous investigations. The use of the kinetic theory allows us to incorporate dissipative corrections (due to the thermal shear and gradients of thermal vorticity) into the Pauli-Lubanski vector that determines spin polarization and can be directly compared with the experimental data. As in earlier similar studies, it turns out that a successful description of data can only be achieved with additional assumptions -- in our case, they involve the use of projected thermal vorticity and a suitably adjusted time for spin relaxation ($\tau_s$). From our analysis, we find that $\tau_s \sim 5$ fm/$c$, which is comparable with other estimates., Comment: 6 pages, 2 figures
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- 2024
19. Circular Photocurrents in Centrosymmetric Semiconductors with Hidden Spin Polarization
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Wang, Kexin, Zhang, Butian, Yan, Chengyu, Du, Luojun, and Wang, Shun
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Centrosymmetric materials with site inversion asymmetries possess hidden spin polarization, which remains challenging to be converted into spin currents because the global inversion symmetry is still conserved. This study demonstrates the spin-polarized DC circular photocurrents (CPC) in centrosymmetric transition metal dichalcogenides (TMDCs) at normal incidence without applying electric bias. The global inversion symmetry is broken by using a spatially-varying circularly polarized light beam, which could generate spin gradient owing to the hidden spin polarization. The dependences of the CPC on electrode configuration, illumination position, and beam spot size indicate an emergence of circulating electric current under spatially inhomogeneous light, which is associated with the deflection of spin-polarized current through the inverse spin Hall effect (ISHE). The CPC is subsequently utilized to probe the spin polarization and ISHE under different excitation wavelengths and temperatures. The results of this study demonstrate the feasibility of using centrosymmetric materials with hidden spin polarization and non-vanishing Berry curvature for spintronic device applications.
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- 2024
20. Intrinsic high-fidelity spin polarization of charged vacancies in hexagonal boron nitride
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Lee, Wonjae, Liu, Vincent S., Zhang, Zhelun, Kim, Sangha, Gong, Ruotian, Du, Xinyi, Pham, Khanh, Poirier, Thomas, Hao, Zeyu, Edgar, James H., Kim, Philip, Zu, Chong, Davis, Emily J., and Yao, Norman Y.
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Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
The negatively charged boron vacancy ($\mathrm{V}_{\mathrm{B}}^-$) in hexagonal boron nitride (hBN) has garnered significant attention among defects in two-dimensional materials. This owes, in part, to its deterministic generation, well-characterized atomic structure, and optical polarizability at room temperature. We investigate the latter through extensive measurements probing both the ground and excited state polarization dynamics. We develop a semiclassical model based on these measurements that predicts a near-unity degree of spin polarization, surpassing other solid-state spin defects under ambient conditions. Building upon our model, we include the presence of nuclear spin degrees of freedom adjacent to the $\mathrm{V}_{\mathrm{B}}^-$ and perform a comprehensive set of Lindbladian numerics to investigate the hyperfine-induced polarization of the nuclear spins. Our simulations predict a number of important features that emerge as a function of magnetic field which are borne out by experiment.
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- 2024
21. Steady state, displacement current and spin polarization for massless fermion in a shear flow
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Lin, Shu and Wang, Ziyue
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High Energy Physics - Phenomenology ,Nuclear Experiment ,Nuclear Theory - Abstract
We consider spin polarization of massless fermions in a shear flow, whose complete contributions contain magnetization current and side-jump current known from collisional chiral kinetic theory. We argue that the side-jump current adopts interpretation of displacement current. We explicitly determine the displacement current contribution in the steady state reached in shear flow for a QED plasma. We find the displacement contribution enhances the magnetization contribution at small and large momenta, but leads to a suppression effect at intermediate momenta. Major differences from previous studies on collisional effect are: (i) the fermions are in the same steady state as the medium rather than being probes; (ii) Compton scattering and pair annihilation are also included in addition to the Coulomb scattering considered before., Comment: 20 pages, 4 figures
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- 2024
22. Randomness in atomic disorder and consequent squandering of spin-polarization in a ferromagnetically fragile quaternary Heusler alloy FeRuCrSi
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Gupta, Shuvankar, Chakraborty, Sudip, Bhasin, Vidha, Barreteau, Celine, Crivello, Jean-Claude, Greneche, Jean-Marc, Jha, S. N., Bhattacharyya, D., Alleno, Eric, and Mazumdar, Chandan
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Condensed Matter - Materials Science - Abstract
Ru$_{2-x}$Fe$_x$CrSi ( 0 $<$ x $<$1) system is theoretically predicted to be one of the very few known examples of robust half-metallic ferromagnet with 100\% spin polarization. Since Cr is considered to be the main contributor to magnetism, the Fe/Ru substitution is not expected to disturb its magnetic properties any significantly, and hence all Fe-containing members of the series are predicted to follow Slater-Pauling rule with a saturation magnetic moment of 2 ${\mu_B}$/f.u. However, contrarily to the theoretical expectations, some experiments rather show a linear variation of the saturation magnetization and Curie temperature with Fe (\textit{x}) substitution. The equiatomic member FeRuCrSi of this family is also considered as a technologically important material, where the band structure calculations suggest the material to be spin gapless semiconductor. Through our in-depth structural analysis of FeRuCrSi using X-ray diffraction, extended X-ray absorption fine structure and $^{57}$Fe M\"{o}ssbauer spectrometry, we found a random disorder between Fe and Ru sites, while the magnetic moment in this system is actually contributed by Fe atoms, questioning the very basic foundation of the half-metallic character proposed by all theoretical calculations on Ru$_{2-x}$Fe$_x$CrSi series. Our M\"{o}ssbauer result also envisions a rather rare scenario where the main physical properties are intricately correlated to the chemistry of the material in the form of random atomic disorder on a localised scale.
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- 2024
23. Field-induced spin polarization in lightly Cr-substituted layered antiferromagnet NiPS3
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Basnet, Rabindra, Upreti, Dinesh, Patel, Taksh, Chhetri, Santosh Karki, Acharya, Gokul, Nabi, Md Rafique Un, Sharma, Manish Mani, Sakon, Josh, Mortazavi, Mansour, and Hu, Jin
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Tuning magnetic properties in layered magnets is an important route to realize novel phenomenon related to two-dimensional (2D) magnetism. Recently, tuning antiferromagnetic (AFM) properties through substitution and intercalation techniques have been widely studied in MPX3 compounds. Interesting phenomena, such as diverse AFM structures and even the signatures of ferrimagnetism, have been reported. However, long-range ferromagnetic (FM) ordering has remained elusive. In this work, we explored the magnetic properties of the previously unreported Cr-substituted NiPS3. We found that Cr substitution is extremely efficient in controlling spin orientation in NiPS3. Our study reveals a field-induced spin polarization in lightly (9%) Cr-substituted NiPS3, which is likely attributed to the attenuation of AFM interactions and magnetic anisotropy due to Cr doping. Our work provides a possible strategy to achieve FM phase in AFM MPX3, which could be useful for investigating 2D magnetism as well as potential device applications.
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- 2024
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24. Engineering Metal Electron Spin Polarization to Regulate p‐Band Center of Se for Enhanced Sodium‐Ion Storage.
- Author
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Wang, Dandan, Chao, Yunfeng, Guo, Kaiyang, Wang, Zhuosen, Yang, Mingxing, Zhu, Jianhua, Cui, Xinwei, and Xu, Qun
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POLARIZED electrons , *SPIN polarization , *METAL-spinning , *SODIUM ions , *CHARGE exchange , *ELECTRON spin , *COPPER - Abstract
Sluggish ion diffusion of large sodium ions is one of the main drawbacks challenging the development of metal selenides‐based anode materials for sodium‐ion batteries (SIBs). A spin‐state regulating strategy is first proposed in this work to lift the p‐band center (ɛp) of Se for a fast Na+ transfer kinetic in (Co,Cu)Se2. By utilizing the electron transfer from Cu to Co, the π‐symmetry t2g of Co is fully occupied to decrease the spin polarization. The resultant electron repulsion between Co and Se weakens Co–Se bond to lift the ɛp of Se. The enhanced sodium adsorption energy effectively accelerates the ion transfer at the active material–electrolyte interface. As a result, the (Co,Cu)Se2/NC electrode exhibits an superior sodium storage performance with a capacity of 445 mAh g−1 at 0.2 A g−1, 312 mAh g−1 at 50 A g−1, and 363 mAh g−1 after 10 000 cycles at 10.0 A g−1. The insight into the working mechanism of regulating spin‐state of metals to lift the p‐band center of Se can provide guidelines for the development of both metal selenides‐based anode material and high‐performance SIBs. [ABSTRACT FROM AUTHOR]
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- 2024
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25. Influence of Photoexcitation Conditions on the Spin Polarization of Nitrogen-Vacancy Centers in Isotopically Enriched Silicon Carbide 6H-28 SiC
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F. F. Murzakhanov, G. V. Mamin, M. A. Sadovnikova, D. V. Shurtakova, O. P. Kazarova, E. N. Mokhov, and M. R. Gafurov
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spin-optical property ,spin initialization ,spin polarization ,electron − paramagnetic resonance ,silicon carbide ,nv− center ,Mathematics ,QA1-939 - Abstract
Spin defects in semiconductors are attracting interest as a material basis for quantum information and computing technologies. In this work, the spin properties of negatively charged nitrogen-vacancy (NV−) centers in a 6H-SiC silicon carbide crystal enriched with the 28 Si isotope were studied by high-frequency (94 GHz) electron paramagnetic resonance (EPR) methods. Due to an optical excitation channel at the NV− centers, it was possible to initialize the electron spin of the defect using a laser source, which led to a significant increase in the intensity of the recorded EPR signal. The dependences of the observed spin polarization were analyzed at different optical excitation wavelengths (λ = 640 – 1064 nm), output power (0 – 500 mW), and temperature (50 – 300 K) of the crystal. The results obtained reveal the optimal experimental conditions for maximizing the efficiency of optical quantum energy transfer to the spin system. This opens up new possibilities for using NV− centers in 6H-SiC to create multi-qubit spin-photon interfaces operating in the infrared region.
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- 2024
- Full Text
- View/download PDF
26. Multi-Orbital Interactions and Spin Polarization in Single Rare-Earth Adatoms
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Kelai, Massine, Reale, Stefano, Robles, Roberto, Lee, Jaehyun, Jyoti, Divya, Ohresser, Philippe, Otero, Edwige, Choueikani, Fadi, Scheurer, Fabrice, Lorente, Nicolás, Choi, Deung-Jang, Singha, Aparajita, and Donati, Fabio
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Surface-adsorbed rare-earth nanostructures are ideal platforms to investigate the interplay between intra-atomic interactions and multi-orbital spin configurations. However, addressing these properties has posed severe experimental and theoretical challenges. Here, we use the orbital selectivity offered by X-ray absorption spectroscopy to quantify the Coulomb integrals of Nd atoms on conductive surfaces, as well as the variation of individual orbital occupation upon cluster nucleation. Using X-ray magnetic circular dichroism we identify magnetic moments of the order of \MK{few tens of}~$\mu_{\rm{B}}$ at the $5d$ orbitals and their magnetic coupling with the $4f$ spins. Our results validate orbital-resolved X-ray spectroscopy as a reliable method for quantifying complex multi-orbital interactions in surface-adsorbed lanthanides.
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- 2024
27. Bright-Dark Exciton Interplay Evidenced by Spin Polarization in CdSe/CdMnS Nanoplatelets
- Author
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Shornikova, Elena V., Yakovlev, Dmitri R., Tolmachev, Danil O., Prosnikov, Mikhail A., Christianen, Peter C. M., Shendre, Sushant, Isik, Furkan, Delikanli, Savas, Demir, Hilmi Volkan, and Bayer, Manfred
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Diluted magnetic semiconductor (DMS) colloidal nanocrystals demonstrate remarkable magneto-optical properties. However, the behavior of circular polarization of their emission in high magnetic fields remains unclear. We measure magneto-optical properties of colloidal CdSe/CdMnS nanoplatelets in high magnetic fields up to 30 T and at cryogenic temperatures. The degree of circular polarization of photoluminescence demonstrates non-monotonous behavior in a magnetic field. In low magnetic fields, the polarization degree is positive, due to an exchange interaction of excitons with localized spins of magnetic Mn ions. The exchange interaction is strong enough to overcome the intrinsic Zeeman splitting, which provides negatively polarized emission in nonmagnetic CdSe/CdS nanoplatelets. After reaching a maximum the polarization degree starts to decrease and reverses the sign to negative in high magnetic fields. The critical magnetic field, in which the sign is reversed, increases when temperature is elevated. We develop a model, which explains this behavior by an interplay of bright and dark exciton recombination.
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- 2024
28. Moir\'e superlattices of antimonene on a Bi(111) substrate with van Hove singularity and Rashba-type spin polarization
- Author
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Nakamura, Tomonori, Chen, Yitao, Nemoto, Ryohei, Qian, Wenxuan, Fukushima, Yuto, Kawaguchi, Kaishu, Mori, Ryo, Kondo, Takeshi, Yamaji, Youhei, Tsuda, Shunsuke, Yaji, Koichiro, and Uchihashi, Takashi
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Moir\'e superlattices consisting of two-dimensional materials have attracted immense attention because of emergent phenomena such as flat band-induced Mott insulating states and unconventional superconductivity. However, the effects of spin-orbit coupling on these materials have not yet been fully explored. Here, we show that single- and double-bilayer antimony honeycomb lattices, referred to as antimonene, form moir\'e superlattices on a Bi(111) substrate due to lattice mismatch. Scanning tunnelling microscopy (STM) measurements reveal the presence of spectral peaks near the Fermi level, which are spatially modulated with the moir\'e period. Angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory calculations clarify the surface band structure with saddle points near the Fermi level, which allows us to attribute the observed STM spectral peaks to the van Hove singularity. Moreover, spin-resolved ARPES measurements reveal that the observed surface states are Rashba-type spin-polarized. The present work has significant implications in that Fermi surface instability and symmetry breaking may emerge at low temperatures, where the spin degree of freedom and electron correlation also play important roles., Comment: 37 pages including Supplementary Information
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- 2024
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29. Exploring Spin Polarization of Heavy Quarks in Magnetic Fields and Hot Medium
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Liu, Zhiwei, Bai, Yunfan, Zheng, Shiqi, Huang, Anping, and Chen, Baoyi
- Subjects
Nuclear Theory ,High Energy Physics - Phenomenology - Abstract
Relativistic heavy-ion collisions give rise to the formation of both deconfined QCD matter and a strong magnetic field. The spin of heavy quarks is influenced by interactions with the external magnetic field as well as by random scatterings with thermal light partons. The presence of QCD matter comprising charged quarks can extend the lifetime and strength of the magnetic field, thereby enhancing the degree of heavy quark polarization. However, the random scatterings with QCD matter tend to diminish heavy quark polarization. In this study, we utilize the Landau-Lifshitz-Gilbert (LLG) equation to investigate both these contributions. Taking into account the realistic evolutions of medium temperatures and the in-medium magnetic fields at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC), we observe that heavy quark polarization is limited by the short lifetime of the magnetic field and the high temperatures of the medium. Furthermore, we explore the mass dependence of quark polarization, revealing that the polarization degree of strange quarks is much larger than that of charm quarks., Comment: 6 pages, 10 figures
- Published
- 2024
30. First‐Principles Study on the Spin Polarization of Single‐Walled Arsenic Nitride Nanotubes Decorated with C, O, Ge, and Se.
- Author
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Zhu, Hanze and Rahman, Mavlanjan
- Subjects
- *
SPIN polarization , *ARSENIC , *GREEN'S functions , *NITRIDES , *SPIN-polarized currents , *DENSITY functional theory , *NANOTUBES , *CARBON nanotubes - Abstract
This article utilizes first‐principles calculations within the density functional theory framework, employing spin generalized gradient approximation, to investigate the spin polarization of arsenic nitride nanotubes (AsNNTs). It is found that AsNNT does not exhibit spin polarization and has a bandgap of 1.05 eV, indicating that it is a semiconductor. Decoration with C, O, Ge, and Se on AsNNT induces spin polarization, resulting in magnetic moments of 1.001, 0.916, 0.770, and 0.967 μB, respectively. Meanwhile, all decorated configurations exhibit narrow bandgap semiconductor properties. Furthermore, the nonequilibrium Green's function method is used to study the spin‐polarized current of AsNNT decorated with C, O, Ge, and Se. It is found that AsNNTs decorated with C, Ge, and Se have relatively small spin current values. Notably, the Se‐decorated AsNNT exhibits the highest degree of spin polarization, with the spin current being nearly fully polarized. [ABSTRACT FROM AUTHOR]
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- 2024
- Full Text
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31. Effects of tensor spin polarization on the chiral restoration and deconfinement phase transitions
- Author
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Bao, Yan-Ru and Feng, Sheng-Qin
- Subjects
High Energy Physics - Phenomenology - Abstract
Effects of tensor spin polarization (TSP) on the chiral restoration and deconfinement phase transitions are studied in Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model. For chiral phase transition, the higher the polarized degree of quark-antiquark pairs under the strong magnetic field, the higher the phase transition temperature. The TSP corrects the position of the critical end point. The small impact of TSP on the phase transition temperature is found for the deconfinement phase transition. On the other hand, we divide the phase space into three ranges based on the phase diagram obtained from the PNJL model: the confinement phase with chiral symmetry broken, the deconfinement phase with restored chiral symmetry, and the confinement phase with restored chiral symmetry (quarkyonic phase). It is found that TSP has only a very small effect on the anisotropic pressure in the deconfined phase with chiral symmetry restored and the quarkyonic phase, but it has a very strong effect on the anisotropic pressure in the confined phase with chiral symmetry broken. This is because TSP is closely related to chiral symmetry. The restoration of chiral symmetry means the dissociation of spin polarization condensate., Comment: 20 pages, 7 figures
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- 2024
32. Extrinsic Contribution to Nonlinear Current Induced Spin Polarization
- Author
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Guo, Ruda, Huang, Yue-Xin, Yang, Xiaoxin, Liu, Yi, Xiao, Cong, and Yuan, Zhe
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Nonlinear spin polarization occurring in the second order of driving electric current is the dominant source of nonequilibrium magnetization in centrosymmetric or weakly noncentrosymmetric nonmagnetic materials, and induces nonlinear spin-orbit torque in magnets. Up to now, only the intrinsic mechanism based on anomalous spin polarizability dipole, which is the spin counterpart of Berry curvature dipole, has been studied, while disorder induced mechanisms are still missing. Here, we derive these contributions, which include not only the anomalous distribution function due to skew scattering and coordinate shift, but also interband coherence effects given by disorder induced spin shift and electric field induced anomalous scattering amplitude. We demonstrate these terms and show their importance in a minimal model. A scaling law for nonlinear current-induced spin polarization is constructed, which may help analyze experimental data in the future.
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- 2024
33. Spin polarization in relativistic heavy-ion collisions
- Author
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Becattini, Francesco, Buzzegoli, Matteo, Niida, Takafumi, Pu, Shi, Tang, Ai-Hong, and Wang, Qun
- Subjects
Nuclear Theory - Abstract
Polarization has opened a new physics chapter in relativistic heavy-ion collisions. Since the first prediction and experimental observation of global spin polarization, a lot of progress has been made in understanding its features, both at experimental and theoretical level. In this paper, we give an overview on the recent advances in this field. The covered topics include a review of measurements of global and local spin polarization of hyperons and the global spin alignment of vector mesons. We account for the basic theoretical framework to describe spin polarization in a relativistic fluid such as the Quark Gluon Plasma, including statistical quantum field theory and local thermodynamic equilibrium, spin hydrodynamics, relativistic kinetic theory with spin and coalescence models., Comment: RevTeX 4, 41 pages, 12 figures, review article as a book chapter for QGP6
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- 2024
34. Study of spin polarization dependence on rapidity, transverse momentum, and azimuthal angle
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Florkowski, Wojciech, Ryblewski, Radoslaw, and Singh, Rajeev
- Subjects
High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
We investigate the spacetime evolution of spin polarization within a hydrodynamic framework based on the de Groot--van Leeuwen--van Weert expressions for energy-momentum and spin tensors. The system's deviation from boost invariance results in the interplay of different spin polarization components, impacting spin observables. We specifically examine the transverse momentum, azimuthal angle, and rapidity dependence of the mean spin polarization vector of $\Lambda$ hyperons. Our results qualitatively align with other models and experimental data on global spin polarization rapidity dependence. While the quadrupole structure is absent in the longitudinal component at midrapidity, our analysis reveals non-trivial signal at forward rapidities that differs from predictions based on the Bjorken expansion., Comment: Contribution to SPIN 2023
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- 2024
35. Weak magnetic effect in quark-gluon plasma and local spin polarization
- Author
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Sun, Jing-An and Yan, Li
- Subjects
Nuclear Theory ,High Energy Physics - Phenomenology ,Nuclear Experiment - Abstract
We propose the weak magnetic effect, which emerges in quark-gluon plasma close to local thermal equilibrium as the dissipative correction to the quark phase space distribution function, as a novel contribution to the observed Lambda hyperon local spin polarization. With a finite field strength, which is consistent with previous estimate of the magnetic field in heavy-ion collisions, one is able to explain the experimentally observed Lambda local spin polarization through all centrality classes. Moreover, the weak magnetic effect plays an unambiguous role in the ordering between the second-order and the third-order modulations of the Lambda local spin polarization in experiments., Comment: Typos corrected
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- 2024
36. The spin polarization strategy regulates heterogeneous catalytic activity performance: from fundamentals to applications.
- Author
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Wang, Yan, Sun, Junkang, Sun, Ning, Zhang, Mengyang, Liu, Xianya, Zhang, Anlei, and Wang, Longlu
- Subjects
- *
SPIN polarization , *CATALYTIC activity , *EVIDENCE gaps , *ENERGY consumption , *ENERGY storage - Abstract
In recent years, there has been significant attention towards the development of catalysts that exhibit superior performance and environmentally friendly attributes. This surge in interest is driven by the growing demands for energy utilization and storage as well as environmental preservation. Spin polarization plays a crucial role in catalyst design, comprehension of catalytic mechanisms, and reaction control, offering novel insights for the design of highly efficient catalysts. However, there are still some significant research gaps in the current study of spin catalysis. Therefore, it is urgent to understand how spin polarization impacts catalytic reactions to develop superior performance catalysts. Herein, we present a comprehensive summary of the application of spin polarization in catalysis. Firstly, we summarize the fundamental mechanism of spin polarization in catalytic reactions from two aspects of kinetics and thermodynamics. Additionally, we review the regulation mechanism of spin polarization in various catalytic applications and several approaches to modulate spin polarization. Moreover, we discuss the future development of spin polarization in catalysis and propose several potential avenues for further progress. We aim to improve current catalytic systems through implementing a novel and distinctive spin engineering strategy. [ABSTRACT FROM AUTHOR]
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- 2024
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37. Boosting the spin polarization and ferromagnetic stability of monolayer C3N through strategic mono-doping and co-doping with copper (Cu) and vanadium (V).
- Author
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Niu, Yong, Wang, Ying, Wang, Pan, and Zhang, Xiaofei
- Subjects
- *
SPIN polarization , *COPPER , *VANADIUM , *MONOMOLECULAR films , *TRANSITION metals - Abstract
The inherently low spin polarization of ferromagnetism in two-dimensional C3N hinders its application in spintronics. Addressing this, the impact of (V, Cu) co-doping on the spin polarization in monolayer C3N has been systemically explored through first-principles calculations. The results reveal that doping with a single V or Cu atom at an N site significantly enhances spin polarization compared to doping at a C site. Moreover, substituting a single C or N atom with a V atom results in significantly enhanced spin polarization compared to replacement with a Cu atom. Significantly, V and Cu co-doping at different N sites in C3N systems uniformly favors ferromagnetic states. A remarkable boost in spin polarization is achieved through strategic co-doping of V and Cu at N sites, separated by a distance of 5.681 Å. This enhancement is attributed to the coupling interactions among the C 2p, N 2p, Cu 3d, and V 3d orbitals. The theoretical investigation suggests an effective route to greatly enhance the spin polarization through targeted 3d transition metal co-doping, contributing to the development of high-performance spintronic devices and advancing quantum computing technologies. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
38. Spin Polarization Enhances the Catalytic Activity of Monolayer MoSe 2 for Oxygen Reduction Reaction.
- Author
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Shu, Dan, Wang, Dan, Wang, Yan, Tang, Liming, and Chen, Keqiu
- Subjects
- *
PROTON exchange membrane fuel cells , *SPIN polarization , *OXYGEN reduction , *CATALYSIS , *CHARGE exchange - Abstract
The key factors in achieving high energy efficiency for proton exchange membrane fuel cells are reducing overpotential and increasing the oxygen reduction rate. Based on first-principles calculations, we induce H atom adsorption on 4 × 4 × 1 monolayer MoSe2 to induce spin polarization, thereby improving the catalytic performance. In the calculation of supercells, the band unfolding method is used to address the band folding effect in doped systems. Furthermore, it is evident from analyzing the unique energy band configuration of MoSe2 that a higher valley splitting value has better catalytic effects on the oxygen reduction reaction. We believe that the symmetries of the distinct adsorption site result in different overpotentials. In addition, when an even number of hydrogen atoms is adsorbed, the monolayer MoSe2 has no spin polarization. The spin can affect the electron transfer process and alter the hybrid energy with the reaction products, thereby regulating its catalytic performance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
39. Regulation of chiral structure and spin polarization by circularly polarized light and electric field in copolymers.
- Author
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Hu, Renjie, Lu, Xiangqian, and Qin, Wei
- Subjects
- *
SPIN polarization , *ELECTRIC lighting , *ELECTRIC fields , *CHIRALITY of nuclear particles , *COPOLYMERS , *ENANTIOMERS , *ELECTRON-phonon interactions , *ELECTRON spin states - Abstract
Combining chirality with ferromagnetism is challenging in organic materials and may bring potential application for the cross-integration of multiple disciplines. In this work, we achieved the intrinsic coexistence of chirality and spontaneous spin polarization in the diblock copolymers, where left-handed and right-handed circularly polarized lights present tunability on both the circular dichroism and spin polarization. Without electron dependence of transport in chiral copolymer, chirality is still coupled with spin. The phenomenon observed here is not the traditional chirality induced spin selectivity effect. Moreover, the electric field could also effectively tune the chirality dependence of circular dichroism to further affect the magnitude of spin polarization. Thus, a strong relationship between the chirality and spin polarization is formed in chiral copolymers. In addition, because of the different molecular packing for chiral enantiomers, electron–phonon coupling strengths are different to lead to a difference in spin polarization. Overall, the properties of chirality, spontaneous spin polarization, and photon-chirality-spin coupling are developed and studied, which effectively promotes the ability of potential applications of chiral copolymers. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
40. Dwell time and spin polarization for electron in single ferromagnetic-stripe device modulated by spin–orbit couplings
- Author
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Li Wen, Mao-Wang Lu, Jia-Li Chen, Sai-Yan Chen, Xue-Li Cao, and An-Qi Zhang
- Subjects
Semiconductor spintronics ,single ferromagnetic-stripe device (SFSD) ,Spin–orbit coupling (SOC) ,Dwell time ,Electron-spin polarization ,Physics ,QC1-999 - Abstract
Considering both Zeeman effect and spin–orbit coupling, we calculate dwell time for electron in single ferromagnetic-stripe device (SFSD), which can be constructed by patterning a nanosized ferromagnetic stripe on the surface of GaAs/AlxGa1-xAs heterostructure. Due to an intrinsic symmetry in the SFSD, dwell time is independent of electron spins, if only Zeeman effect is involved. However, the intrinsic symmetry is broken by spin–orbit coupling, which gives rise to spin-dependent dwell time for electron in the SFSD. As a result, electron spins can be separated in time dimension, which induces an obvious electron-spin polarization effect in the SFSD. Spin polarization ratio can be efficaciously modified by interfacial confining electric-field or strain engineering, which attributes to the dependence of effective potential felt by electron in the SFSD on spin–orbit couplings. Thus, the SFSD can act as a controllable temporal electron-spin splitter, a class of electron-spin polarized sources in semiconductor spintronics.
- Published
- 2024
- Full Text
- View/download PDF
41. Reproduction of single-to-double hysteresis transition of nuclear spin polarization in a single InAlAs quantum dot.
- Author
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Li, Z.-R., Yamamoto, S., Adachi, S., and Kaji, R.
- Abstract
We have observed a transition from single to double hysteresis of nuclear spin polarization (NSP) with increasing magnetic field in a single InAlAs self-assembled quantum dot, which means the birth of a third stable branch that depends on the field strength. This NSP transition behavior could not be reproduced by standard model calculations using a fixed electron–nuclear spin correlation time τ c under different external field conditions. By introducing the field dependence of τ c , we were able to successfully reproduce the observed NSP transition. This finding on the phenomenological description of the magnetic field dependence will be a future highlight of τ c . [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. Electron Spin Dynamics of the Photoexcited Triplet States of Bromoperylenebisimide Compounds: Computation and Analysis of the Electron Spin Polarization Evolution in TREPR Spectra
- Author
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Mambetov, A., Sukhanov, A., Zhang, Xue, Zhao, Jianzhang, and Voronkova, V.
- Published
- 2024
- Full Text
- View/download PDF
43. Surface Spin Polarization in the Magnetic Response of GeTe Rashba Ferroelectric
- Author
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Avakyants, A. A., Orlova, N. N., Timonina, A. V., Kolesnikov, N. N., and Deviatov, E. V.
- Published
- 2024
- Full Text
- View/download PDF
44. Inducing spin polarization via Co doping in the BiVO4 cell to enhance the built-in electric field for promotion of photocatalytic CO2 reduction.
- Author
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Liu, Yujia, Deng, Qucheng, Yao, Zuofang, Liang, Ting, Zhang, Shiming, Zhu, Tingting, Xing, Chenchen, Pan, Jinghui, Yu, Zebin, Liang, Keying, Xie, Tao, Li, Rui, and Hou, Yanping
- Subjects
- *
SPIN polarization , *PHOTOREDUCTION , *ELECTRIC fields , *KELVIN probe force microscopy , *CHARGE carrier lifetime , *PHOTOELECTROCHEMISTRY - Abstract
[Display omitted] The efficiency of CO 2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO 4 cell to boost photocatalytic CO 2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co-doped BiVO 4 were enhanced. CO production during CO 2 photocatalytic reduction from the Co-BiVO 4 was 61.6 times of the BiVO 4. Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO 2 reduction from the Co-BiVO 4 , with 68.25 folds improvement of CO production compared to pristine BiVO 4. The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO 4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO− was a crucial intermediate in the process of CO 2 RR, and possible pathways for CO 2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Amorphous Gallium Oxide Nanosheets with Broad Absorption and Spin Polarization for Si‐Based UV‒Vis‒NIR Photodetectors.
- Author
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Yu, Junling, Wu, Geng, Han, Xiao, Liu, Peigen, You, Su, Yang, Qing, and Hong, Xun
- Subjects
- *
SPIN polarization , *EXTENDED X-ray absorption fine structure , *PHOTODETECTORS , *GALLIUM , *WIDE gap semiconductors - Abstract
Achieving broad light absorption and high carrier separation efficiency is crucial for wide‐bandgap semiconductors to enable broadband photodetection applications. Here, amorphous gallium oxide nanosheets feature with broad absorption and spin polarization Wis synthesized, and assembled with graphene and p‐Si, realizing UV‒vis‒NIR photodetection. Extended X‐ray absorption fine structure reveals that a‐GaOx NSs possess lower tetrahedral Ga occupation (10%) compared to crystalline β‐Ga2O3 (50%). UV‒vis‒NIR diffuse reflectance spectra and magnetic hysteresis loops demonstrate broad absorption and weak ferromagnetism of a‐GaOx NSs, respectively. Density functional theory calculation further reveals sub‐gap states and spin polarization in a‐GaOx NSs. Moreover, combined with Mott–Schottky curves, photoluminescence and time‐resolved photoluminescence spectra inferred the effective suppression of carrier recombination via spin polarization of a‐GaOx NSs. The graphene/a‐GaOx NSs/p‐Si photodetector incorporates a back‐to‐back rectifying junction, acquiring a dark current as low as 63 pA. All photogenerated carriers are in the depletion region of the photodetector favouring efficient charge separation. This photodetector exhibits a response time of τrise<60 ms and τfall<120 ms, and high specific detectivity 1013 Jones over 254–1064 nm light. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
46. Antiparallel Spin Polarization and Spin Current Induced by Thermal Current and Locally Broken Inversion Symmetry in a Double-Quantum Well Structure.
- Author
-
Yuta Suzuki, Yuma Kitagawa, Shin-ichiro Tezuka, and Hiroshi Akera
- Subjects
- *
SPIN polarization , *INDUCED polarization , *NUCLEAR spin , *BOLTZMANN'S equation , *ELECTRON density , *NON-equilibrium reactions , *SYMMETRY breaking , *SPIN-orbit interactions - Abstract
Generating a nonequilibrium spin polarization with a driving force is first realized by the electric current in a system with broken inversion symmetry and extended to that induced by the thermal current and that appearing in an inversionsymmetric system with locally broken inversion symmetry. This article theoretically explores the spin polarization generated by the thermal current and the locally broken inversion symmetry in a symmetric double-quantum well structure (DQWS). This thermally induced spin polarization (TISP) appears in the antiparallel configuration with the TISP of two wells in opposite directions. The calculation using the Boltzmann equation in the relaxation-time approximation under the condition of zero charge current shows that the local TISP exhibits the maximum at a finite Rashba spin-orbit interaction when the electron density is fixed. This is because the local TISP in the DQWS is enhanced at the chemical potential near the bottom of the first-excited sub-band. This enhancement also occurs in a single quantum well with globally broken inversion symmetry. Another finding is that the maximum of the local TISP appears at a nonzero interwell coupling. The spin current by the diffusion of the local TISP into an adjacent electrode is also calculated. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
47. Enhancing Intramolecular Ferromagnetic Coupling in Tetrathiafulvalene–Nitronyl Nitroxide‐Based Compounds through Spin Polarization Mechanism.
- Author
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Franquesa‐Viñas, Pau, Ribas‐Ariño, Jordi, Santiago, Raul, and Deumal, Mercè
- Subjects
- *
SPIN polarization , *ENHANCED magnetoresistance , *MAGNETIC coupling , *RADICALS (Chemistry) , *ELECTRON donors , *MOLECULAR crystals , *FISH meal - Abstract
Spin‐polarized donor radicals based on tetrathiafulvalene (TTF) derivatives and nitronyl nitroxide (NN) radicals in which one‐electron oxidation involves the HOMO instead of the SOMO are well known for exhibiting magnetoresistance. In particular, BTBN consists of one dibromo‐TTF and one NN radical, which are linked by a phenyl coupler group. One of the key factors driving magnetoresistance is the presence of intramolecular ferromagnetic (FM) coupling between the oxidized π‐donor (TTF+⋅, D unit) and NN (R unit). Here, a theoretical study is carried out to assess suitable candidates with enhanced FM coupling with respect BTBN, which is thus used as a reference. The study is conducted via in silico chemical modification of the substituents of the BTBN basic functional units (D and R radicals, C coupler) to benefit from the spin polarization mechanism to boost the intramolecular FM coupling, aiming to distort the BTBN radical arrangement within the molecular crystal as little as possible, in the event the material can be synthesized. NICSiso(1) and Wiberg's Bond Order are analyzed to further assist in identifying promising potential candidates, since the decrease in aromaticity is expected to enhance the diradical character and give rise to a larger magnetic coupling value. The most favorable diradical building block to replace the BTBN moiety results from using a hydroxyl‐ethylene (−(H)C=C(OH)−) as a coupler preserving BTBN original radicals, namely, NN and TTF+⋅ units. This study aims at illustrating the feasibility of improving the intramolecular FM interaction between radical moieties, which is fully realized, as a first step towards the synthesis of new materials with (possibly) enhanced magnetoresistance properties. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
48. Vacancy engineering modulates spin polarization to enhance the charge dynamics of CuIn5S8 for photocatalytic sterilization.
- Author
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Wu, Wenbin, Wang, Jing, Liang, Xiaojie, Luo, Laixi, Yang, Yaohong, Zhou, Fan, Deng, Shuduan, Song, Yumin, Yang, Le, and Kang, Kunyong
- Subjects
- *
STERILIZATION (Disinfection) , *SPIN polarization , *ELECTRON paramagnetic resonance , *ESCHERICHIA coli , *IRRADIATION , *WATER disinfection , *RADIATION sterilization - Abstract
Photocatalytic sterilization technology is a strategy that is environmentally friendly for killing drug-resistant bacteria using solar energy. The role of reactive oxygen species (ROS) required for sterilization depends on the charge separation properties of the photocatalyst. Therefore, we modified the photocatalytic performance of CuIn5S8 by fabricating S-vacancies based on the work function (Φ) theory. The spin state density calculations show that S-vacancies lead to spin polarization, and it is easier to separate electrons and holes when their spin directions change. Electron paramagnetic resonance (EPR) results show that Vs-CuIn5S8-3 can produce more ROS. Under visible light irradiation, Vs-CuIn5S8-3 killed 99% of E. coli and MRSA in natural water within 30 minutes. The work adopted S-vacancies to regulate spin polarization and improve photocatalytic activity, which has great potential in natural water disinfection. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. Orientation-dependent spin-polarization and transport properties in altermagnet based resonant tunneling junctions
- Author
-
Kai-Yi Lyu and Yu-Xian Li
- Subjects
Altermagnet ,Spin split ,Transmission ,Orientation-dependent ,Spin-polarization ,Conductance ,Physics ,QC1-999 - Abstract
We investigate the spin-dependent spin-polarization and transport properties in altermagnet-based resonant tunneling junctions, in which the altermagnet has two symmetric orientations of spin-split Fermi surface. In the first model the Fermi surface is an ellipse with the major axes either parallel or perpendicular to the altermagnet/barrier interface, and the Fermi surface in the second one is also an ellipse but the major and the minor axes have the same angle relative to the altermagnet/barrier interface. Our findings reveal that the transport properties for spin-up and spin-down electrons are spin polarized and depend on the orientation of the altermagnet with respect to the interface. In contrast to conventional ferromagnetic and antiferromagnetic splitting mechanisms, the transmission in our study exhibits spin splitting with an alternating sign. For the first model, the total spin-polarization is zero, indicating a lack of net magnetization due to the combined effects of spin and real-space symmetries, thereby reflecting normal metal properties. Conversely, in the second model, a discernible total spin-polarization emerges, indicative of ferromagnetism. These orientation-dependent transport properties exemplify the unique features of the altermagnetism. The anisotropic altermagnetic state in momentum space can be measured by the orientation-dependent conductance in these resonant tunneling junctions.
- Published
- 2024
- Full Text
- View/download PDF
50. Observation of a non-trivial in-plane field-like torque due to out-of-plane spin polarization in Al/Ni80Fe20/AlOx heterostructures.
- Author
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Mudgal, Richa, Gupta, Pankhuri, Das, Samaresh, and Muduli, P. K.
- Subjects
- *
SPIN polarization , *TORQUE , *HETEROSTRUCTURES , *HALL effect , *FERROMAGNETIC resonance - Abstract
We performed spin-torque ferromagnetic resonance studies on the Al/NiFe/AlOx heterostructure. We observed a large non-trivial field-like torque, τ FL z , due to the out-of-plane spin polarization, despite the lack of heavy metal in our multilayer. The torque conductivity is found to be significant with a value equal to σ FL z = (21 ± 2) ℏ 2 e × 10 3 Ω − 1 m − 1 . From a detailed Al thickness dependence, we show that τ FL z arises from the interface between Al and NiFe. We demonstrate that the observed τ FL z arises from the spin-swapping mechanism at the Al/NiFe interface rather than the orbital Hall effect of Al. This observation of a non-trivial spin–orbit torque in the low-cost light element, Al, is highly significant for the energy-efficient control of spintronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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