Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C39: Spin-orbit Coupling in SemiconductorsFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DCMP DMP Chair: Vlad Pribiag, University of Minnesota Room: BCEC 207 |
Monday, March 4, 2019 2:30PM - 3:06PM |
C39.00001: Asymmetric g Tensor in Low-Symmetry Two-Dimensional Hole Systems Invited Speaker: Roland Winkler Zeeman coupling characterized by the g factor is a key ingredient to developing novel spin-based technologies such as quantum information protocols. In low-symmetry systems, the g factor becomes a second-rank tensor (a 3×3 matrix) that couples the spin to the magnetic field B. It has long been believed that this tensor g only affects the energy splitting in a magnetic field. We demonstrate [1] that it also encodes the direction of the axis about which the spins precess in the external field B. In general, this axis is not aligned with B. Using time-resolved Kerr rotation measurements performed on a sequence of low-symmetry two-dimensional hole systems in GaAs/AlAs quantum wells, we show that this feature of the tensor g manifest itself in unusual precessional motion as well as distinct dependencies of hole spin dynamics on the direction of the magnetic field B. A detailed theoretical analysis of these experiments allows us, for the first time, to determine the individual components of the full tensor g for [113]-, [111]- and [110]-grown samples. We also derive transparent analytical expressions for the components of the tensor g, complemented with accurate numerical calculations yielding very good agreement between experiment and theory. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C39.00002: Enhancement of the Spin-Orbit Coupling in Silicon by Bismuth Doping Fabien Rortais, SOOBEOM LEE, Ryo Ohshima, Sergey Dushenko, Yuichiro Ando, Masashi Shiraishi Si possesses a low spin-orbit coupling, it allows a long spin lifetime but limits new device-designing possibilities in spintronics, particularly with the spin-charge conversion effects to create an all-Si spin devices. The purpose of this study is to create a sizable spin-orbit interaction in Si by implantation of a heavy element, bismuth (Bi). |
Monday, March 4, 2019 3:18PM - 3:30PM |
C39.00003: Strain engineering of Rashba-Dresselhaus spin-orbit coupling and intrinsic spin-Hall effect in Si Paul C Lou, Anand Katailiha, Ravindra G Bhardwaj, Sandeep Kumar The weak intrinsic spin-orbit coupling and centosymmetric crystal structure are critical bottleneck in development of Si spintronics because it leads to insignificant spin-Hall effect (spin current generation) and inverse spin-Hall effect (spin current detection) even though it results into long spin diffusion length at room temperature. In this experimental study, we use strain gradient to break the structural inversion symmetry, which causes flexoelectric effect and charge separation. This leads to the Rashba-Dresselhaus spin orbit coupling in the bulk of Si along with Si interface. The cubic Rashba-Dresselhaus spin-orbit coupling lifts the spin degeneracy of band structure introducing intrinsic spin-Hall effect, which is uncovered using spin-Hall magnetoresistance measurement in Ni80Fe20/MgO/p-Si freestanding thin film. The strain gradient effects are uncovered using piezoresistive behavior due to thermal expansion induced compressive stresses. The intrinsic spin-Hall effect is observed in both n-doped and p-doped Si thin films. This experimental study brings the Si spintronics closer to reality. This work demonstrates that strain gradient can be used for spin current generation, detection and control in Si. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C39.00004: ABSTRACT WITHDRAWN
|
Monday, March 4, 2019 3:42PM - 3:54PM |
C39.00005: Unidirectional magnetoresistance in a bulk Rashba ferromagnet Ryutaro Yoshimi, Kenji Yasuda, Atsushi Tsukazaki, Minoru Kawamura, Kei Takahashi, Masashi Kawasaki, Yoshinori Tokura The Rashba effect is the spin band splitting due to broken inversion symmetry through spin-orbit coupling, typically observed at surfaces and interfaces. Recently, some noncentrosymmetryic crystals have been found to have the bulk Rashba bands that are larger than surface/interface ones. Nonreciprocal transport of quantum particles such as electron, spin and phonon is known to occur by further breaking time reversal symmetry in such a material without inversion symmetry. In particular, the interplay with magnetism in spin-polarized bands may enhance the nonreciprocal charge transport. In this study, we investigated the unidirectional magnetoresistance in thin films of Ge1-xMnxTe, which is a bulk ferromagnetic Rashba semiconductor. The magnitude of nonreciprocal transport shows a strong dependence on carrier density, which suggests that the scattering process on Fermi surface is essential for the nonreciprocal transport in the system. |
Monday, March 4, 2019 3:54PM - 4:06PM |
C39.00006: The temperature and doping dependence of inverse spin Hall effect in n-GaAs Zhen Jiang, Sahil Patel, Paul Crowell, Chris Palmstrom We have carried out measurements of the inverse spin Hall effect (ISHE) in a series of n-GaAs epilayers doped near the metal-insulator transition. Spin currents are generated using epitaxial Fe/GaAs (001) Schottky tunnel barriers. The ISHE is detected in a simple Hall cross geometry, and precession in a static magnetic field (the Hanle effect) is used to separate the effect from background contributions. We find that the ISHE voltage at low temperatures is much larger than expected based on previous measurements of the direct spin Hall effect. The enhancement is accompanied by significant distortion of the Hanle curves, suggesting that hyperfine interactions play a significant role. Comparison with non-local spin valve measurements over the entire doping range (3 x 10^16 cm^-3 to 7 x 10^16 cm^-3) and at temperatures up to 110 K indicates that local inhomogeneities in the hyperfine field, which disappear as the temperature increases, may be responsible for the enhancement. |
Monday, March 4, 2019 4:06PM - 4:18PM |
C39.00007: Time resolved spectroscopy of n-type InAsP films Rathsara R Herath Mudiyanselage, Brenden A Magill, Giti Khodaparast, Joseph A Spencer, Kiara McMillan, Sukgeun Choi, Chris Palmstrom In this study, we employed ultrafast Time Resolved Differential Reflectivity (TRDR) and ultrafast time resolved Magneto-optic Kerr Effect (MOKE) on InAsxP1-x ternary alloy. In recent years, InAsxP1-x ternary alloys have attracted extensive attention due to the immense prospect for various optoelectronic applications including optical telecommunication, broadband photodetectors, mid-IR lasers, and also quantum communication devices. 1,2 As the switching rates in devices are pushed to higher frequencies in optoelectronic and spintronic devices, it is required to perform comprehensive studies of the carrier and spin relaxation dynamics in semiconductors on a femto-second timescale. Here we report carrier and spin dynamics of n-type InAsxP1-x films in a broad optical region (700 nm and 1000 nm). Also, we observed the generation of coherent oscillations which could be related to photo-induced coherent acoustic phonons. The InAsxP1-x films are ~1.2 micron thick grown on semi-insulating InP (001) wafers and the carrier concentrations are estimated to be 1x1017 cm--3. |
Monday, March 4, 2019 4:18PM - 4:30PM |
C39.00008: Protected Hidden Spin Polarization by Crystalline Symmetry in Centrosymmetric Nonmagnetic Systems Yingjie Zhang, Qihang Liu We derive a tight-binding model with spin-orbital interaction to describe the band edge behaviors of a two-dimensional centrosymmetric system with non-symmorphic symmertry. The two sublattices in this structure are staggered along the normal direction, and connect each other by glide reflection operations, which plays an essential role in protecting the local Rashba spin polarization for each sublattice. By model simulation and symmetry analyses, we find that each sublattice hosts a Rashba-type spin polarization due to the local dipole field. Taking the sublattice interaction into account, The spin texture of the two sublattices around the corner of Brillouin zone still present remarkable Rashba-type vortex with exactly opposite patterns to each other, while at the Gamma point the interaction between two sublattices tends to cancel the local spin polarization. Our finding provides a promising avenue to search material candidates with strong hidden spin polarization, and thus broadens the type of materials that can be used for novel spintronic applications. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C39.00009: Uncovering and tailoring hidden Rashba spin-orbit coupling in centrosymmetric crystals Linding Yuan, Qihang Liu, Xiuwen Zhang, Jun-Wei Luo, Shu-Shen Li, Alex Zunger Hidden Rashba and Dresselhaus spin-splittings in centrosymmetric crystals having subunits (sectors) with non-centrosymmetric symmetries (the R-2 and D-2 effects) have been predicted and observed experimentally, but the microscopic mechanism remains unclear. Here we demonstrate that the spin-splitting in R-2 is enforced by the non-symmorphic symmetry of the wavevectors, which ensures that the pertinent spin wavefunctions segregate spatially on just one of the two inversion-partner sectors and thus avoid compensation. This finding establishes a common fundamental source for the conventional non-centrosymmetric Rashba (R-1) effect and the R-2 effect, both originating from the local sector symmetries, rather than from the global crystal symmetry per se. We further show that the effective Hamiltonian for the R-1 effect is also applicable for the R-2 effect, but applying a symmetry-breaking electric field to an R-2 compound produces different spin-splitting pattern than applying a field to a trivial (non-R-2) centrosymmetric compound. |
Monday, March 4, 2019 4:42PM - 4:54PM |
C39.00010: Ubiquitous Spin-Orbit Coupling in a Screw Dislocation with High Spin Coherency Lin Hu, Huaqing Huang, Zhengfei Wang, Wei Jiang, Xiaojuan Ni, Yinong Zhou, V Zielasek, Max G Lagally, Bing Huang, Feng Liu We theoretically demonstrate that screw dislocation (SD), a 1D topological defect widely present in semiconductors, exhibits ubiquitously a new form of spin-orbit coupling (SOC) effect. Differing from the widely known conventional 2D Rashba-Dresselhaus (RD) SOC effect that typically exists at surfaces or interfaces, the deep-level nature of SD-SOC states in semiconductors readily makes it an ideal SOC. Remarkably, the spin texture of 1D SD-SOC, pertaining to the inherent symmetry of SD, exhibits a significantly higher degree of spin coherency than the 2D RD-SOC. Moreover, the 1D SD-SOC can be tuned by ionicity in compound semiconductors to ideally suppress spin relaxation, as demonstrated by comparative first-principles calculations of SDs in Si/Ge, GaAs, and SiC. Our findings therefore open a new door to manipulating spin transport in semiconductors by taking advantage of an otherwise detrimental topological defect. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C39.00011: Ubiquitous Spin-orbit Coupling in a Screw Dislocation of Semiconductors Bing Huang, Lin Hu, Feng Liu We demonstrate that screw dislocation (SD), a 1D topological defect widely present in semiconductors, exhibits ubiquitously a new form of spin-orbit coupling (SOC) effect. Differing from the widely known conventional 2D Rashba-Dresselhaus (RD) SOC effect that typically exists at surfaces/interfaces, the deep-level nature of SD-SOC states in semiconductors readily makes it an ideal SOC. Remarkably, the spin texture of 1D SD-SOC, pertaining to the inherent symmetry of SD, exhibits a significantly higher degree of spin coherency than the 2D RD-SOC. Moreover, the 1D SD-SOC can be tuned by ionicity in compound semiconductors to ideally suppress spin relaxation, as demonstrated by comparative first-principles calculations of SDs in Si/Ge, GaAs, and SiC. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C39.00012: Extreme asymmetry of 90-degree domain walls in multilayered films of (Ga,Mn)(As,P) Vitalii Vlasko-Vlasov, Wai-Kwong Kwok, Sining Dong, Xinyu Liu, Malgorzata Dobrowolska, J K Furdyna We image the magnetic domain structure during remagnetization of MBE grown multilayered films of a diluted magnetic semiconductor (Ga,Mn)(As,P) with digital modulations of the phosphorus concentration. The samples show two in-plane easy magnetization axes corresponding to the <100> cubic and [110] uniaxial anisotropies, typical for the GaMnAs system. Their remagnetization occurs in two steps through the nucleation and growth of 90-degree domains. Unexpectedly, the domain boundaries align precisely with the easy axes in contrast to our micromagnetic calculations using the measured magnetic parameters of the samples. We discuss how such totally asymmetric Neel domain walls can appear due to Dzyaloshinskii-Moriya interactions enhanced by the multiple sharp interfaces in the multilayered films. |
Monday, March 4, 2019 5:18PM - 5:30PM |
C39.00013: Large perpendicular magnetic anisotropy and anisotropic electronic structure of the new ferromagnetic semiconductor (Ba,K)(Zn,Mn)2As2 single crystal studied by angle-dependent x-ray magnetic circular dichroism Shoya Sakamoto, Guoqiang Zhao, Goro Shibata, Zheng Deng, Kan Zhao, Bijuan Chen, Yosuke Nonaka, Keisuke Ikeda, Zhendong Chi, Yuxuan Wan, Masahiro Suzuki, Tsuneharu Koide, Sadamichi Maekawa, Yasutomo J Uemura, Changqing Jin, Atsushi Fujimori (Ba,K)(Zn,Mn)2As2 is a new ferromagnetic semiconductor isostructural to 122-type Fe-based superconductors. The Curie temperature (TC) reaches 230 K for polycrystalline samples exceeding the highest TC = 200 K of (Ga,Mn)As. In relation to the anisotropic crystal structure, this material has large perpendicular magnetic anisotropy. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700