Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R42: Spins in Semiconductors, Hyperfine and Spin-Orbit CouplingFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DMP DCOMP FIAP Chair: Gian Salis, IBM Zurich Room: 389 |
Thursday, March 16, 2017 8:00AM - 8:12AM |
R42.00001: Characterization of spin-orbit fields in InGaAs quantum wells Gian Salis, Tobias Henn, Lukas Czornomaz Narrow-gap semiconductors exhibit strong spin-orbit interaction and are therefore of interest for spin-based quantum devices and for Majorana zero modes. We investigate coherent electron-spin dynamics and the size and symmetry of spin-orbit interaction in InGaAs/InAlAs quantum wells from 10 K to room temperature using time-resolved Kerr rotation. The spin lifetime exceeds 1\,ns at 10\,K and decreases with temperature. By imprinting a diffusive velocity on the measured electron spins [1], the spin-orbit energy is measured as a change in spin precession frequency. A Rashba symmetry of the spin-orbit interaction is determined with a Rashba coefficient of 2$\times$10$^{-12}$\,eVm [2]. This technique can be applied to other narrow-gap semiconductors without the need to lithographically process the sample or to apply electrical signals.\newline [1] M.~Kohda {\em et al.}, Appl.~Phys.~Lett.~{\bf 107}, 172402 (2015).\newline [2] T. ~Henn {\em et al.}, Appl.~Phys.~Lett.~{\bf 109}, 152104 (2016).\newline [Preview Abstract] |
Thursday, March 16, 2017 8:12AM - 8:24AM |
R42.00002: Current-induced spin polarization in InGaAs and GaAs epilayers as a function of doping density Marta Luengo-Kovac, Simon Huang, Davide Del Gaudio, Jordan Occena, Rachel Goldman, Vanessa Sih Current induced spin polarization (CISP) is a phenomenon in which an applied electric field produces a bulk spin polarization. We performed crystal-axis dependent measurements of CISP and spin-orbit (SO) splitting in seven Si-doped In$_x$Ga$_{1-x}$As samples with different Indium concentrations and doping densities. In all samples, we found a negative differential relationship between the magnitude of the CISP and SO splitting. Since this is contrary to what is predicted by the Rashba-Edelstein equation, which includes only intrinsic SO contributions, we conclude that extrinsic polarization mechanisms dominate. This is corroborated by temperature-dependent spin dephasing time measurements, which show that the contribution from the extrinsic Elliot-Yafet dephasing mechanism is comparable to or greater than the contribution from the intrinsic D’yakonov-Perel’ dephasing mechanism. It is also consistent with measurements performed on GaAs, in which we measured CISP despite the samples having no measurable SO fields. We also found that samples with larger doping densities and Indium concentrations had greater CISP, consistent with our expectations. [Preview Abstract] |
Thursday, March 16, 2017 8:24AM - 8:36AM |
R42.00003: Driving Pure Spin Currents With Dynamic-Nuclear-Polarization Gradients Nicholas Harmon, Michael Flatt\'e Gradients in dynamic nuclear polarization naturally develop near donor atoms in doped semiconductors, like n-GaAs, that are pumped with electronic spin polarization. Recent work has demonstrated that the nuclear gradients play a role in spin dynamics and spin relaxation [1,2]. We predict a new type of spin current to occur when an external magnetic field is appropriately aligned with the gradient of a dynamically polarized nuclear field. In such cases, a linear spin-split dispersion appears in the Landau Hamiltonian which gives rise to a spin-dependent velocity that separates opposite spins and produces a pure spin current. Unlike the spin Hall effect with spin Hall conductivities much less than the charge conductivity, our gradient-driven spin current utilizes the charge conductivity. We propose optical orientation experiments to demonstrate this outcome. [1] N. J. Harmon, T. A. Peterson, C. C. Geppert, S. J. Patel, C. J. Palmstrøm, P. A. Crowell, and M. E. Flatt\'e, Phys. Rev. B 92, 140201(R) (2015). [2] Y.-S. Ou, Y.-H. Chiu, N. J. Harmon, P. Odenthal, M. Sheffield, M. Chilcote, R. K. Kawakami, and M. E. Flatt\'e, Phys. Rev. Lett. 116, 107201 (2016). [Preview Abstract] |
Thursday, March 16, 2017 8:36AM - 9:12AM |
R42.00004: Prolonging the quantum coherence of semiconductor spins Invited Speaker: Edwin Barnes Powerful future technologies based on electronic spins in semiconductors require an unprecedented level of control over the spins. One of the greatest challenges in achieving this control is the decoherence induced by the environment, a problem which is particularly severe in the context of nanoscale quantum devices. In this talk, I will present recent progress in understanding quantitatively the primary sources of decoherence for spins in semiconductor nanostructures, namely the hyperfine interaction with nuclear spins and charge fluctuations. I will present new theoretical techniques that capture the effects of multiple noise sources on the evolution of the spin coherence and show how they can be used to develop new ways to characterize and mitigate noise. I will then describe a new general theory for combatting decoherence by driving the system in such a way that decoherence effects destructively interfere and cancel out, enabling precise and robust control of a broad range of coherent quantum systems. [Preview Abstract] |
Thursday, March 16, 2017 9:12AM - 9:24AM |
R42.00005: Manipulation of coherent spin dynamics using magnetic focusing in spin-orbit-coupled nanostructures Shun-Tsung Lo, Chin-Hung Chen, Ju-Chun Fan, Luke Smith, Graham Creeth, Che-Wei Chang, Michael Pepper, Jonathan Griffiths, Ian Farrer, Harvey Beere, Geb Jones, Dave Ritchie, Tse-Ming Chen Spin-orbit interaction is one of the key ingredients to achieving full control of coherent spin dynamics without relying on ferromagnetism. Previously, the inability to spatially separate electrons with up and down spins has limited the ability to track and use their individual spin dynamics, and hampered the versatility of a spin-orbit-coupled material in both fundamental research and device design. In this work, we demonstrate that the spatial spin splitting of a coherent beam of electrons can be realized using the interplay between an external magnetic field and spin-orbit interactions in semiconductor nanostructures. The technique of transverse magnetic focusing is utilized to probe the spin separation. Furthermore, our ability to tune spin-orbit interactions not only makes the separation between them controllable but also enables us to individually manipulate the coherent spin dynamics of each spin species and hence their correlation. This spin focusing technique paves a way to access and manipulate two spin species simultaneously, which could be essential for spin-based quantum information processing. [Preview Abstract] |
Thursday, March 16, 2017 9:24AM - 9:36AM |
R42.00006: Spin decoherence and dephasing in metal organic perovskites N. Gundlach, P. Odenthal, Y. Yao, C. Zhang, D. Sun, ZG. Yu, Z. V. Vardeny, Y. S. Li Metal organic perovskites have recently generated significant interest, particularly for photo-galvanics. Experimental results have shown several characteristics of perovskite materials that make them viable for spintronic applications. Our previous research has revealed that CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ exhibits a long spin lifetime, and determined the electron and hole g-factors. Further study revealed a nonmonotonic dependence of the ensemble transverse spin lifetime T$_{\mathrm{2}}^{\mathrm{\ast }}$ on applied transverse magnetic field. While g-factor distribution leads to spin dephasing that generally decreases T$_{\mathrm{2}}^{\mathrm{\ast }}$ with increasing transverse magnetic field, the nonmonotonic dependence suggests that carrier spin dynamics are strongly affected by internal local magnetic fields. We will present our systematic study of the spin lifetimes in transvers and longitudinal magnetic fields, and discuss possible factors that contribute to spin decoherence and dephasing in the lead-halide perovskites. We acknowledge funding from the University of Utah and the Department of Energy Office of Science (DE-SC0014579). [Preview Abstract] |
Thursday, March 16, 2017 9:36AM - 9:48AM |
R42.00007: Dissipationless transport of spin-polarized electrons and Cooper pairs in an electron waveguide J. Levy, A. Annadi, S. Lu, G. Cheng, A. Tylan-Tyler, M. Briggeman, M. Tomczyk, M. Huang, D. Pekker, P. Irvin, H. Lee, J.-W. Lee, C.-B. Eom Electron systems undergo profound changes in their behavior when constrained to move along a single axis. To date, clean one-dimensional (1D) electron transport has only been observed in carbon-based nanotubes and nanoribbons, and compound semiconductor nanowires. Complex-oxide heterostructures can possess conductive two-dimensional (2D) interfaces with much richer chemistries and properties, e.g., superconductivity, but with mobilities that appear to preclude ballistic transport in 1D. Here we show that nearly ideal 1D electron waveguides exhibiting ballistic transport of electrons and non-superconducting Cooper pairs can be formed at the interface between the two band insulators LaAlO$_3$ and SrTiO$_3$. The electron waveguides possess gate and magnetic-field selectable spin and charge degrees of freedom, and can be tuned to the one-dimensional limit of a single spin-polarized quantum channel. The strong attractive electron-electron interactions enable a new mode of dissipationless transport of electron pairs that is not superconducting. The selectable spin and subband quantum numbers of these electron waveguides may be useful for quantum simulation, quantum informatio [Preview Abstract] |
Thursday, March 16, 2017 9:48AM - 10:00AM |
R42.00008: Spin-Orbit Assisted Chiral-Tunneling at semiconductor tunnel junctions. Study with advanced 30-band k. p methods. HENRI JAFFRES, THI HUONG DANG, EKATERINA ERINA, VIATCHESLAV SAFAROV, HOAI NGUYEN, HENRI-JEAN DROUHIN We report on theoretical investigations and advanced k.p calculations of carrier forward scattering asymmetry vs. their incidence through interfaces and magnetic tunnel junctions (MTJ) made of semiconductors involving spin-orbit interactions (SOI). This study represents an extension to our previous contribution1 dealing with the role, on the electronic forward scattering asymmetry of the Dresselhaus interaction in the conduction band (CB) of MTJs. The role of the atomic-SOI of semiconductors is investigated afterwardsWe first developed a perturbative scattering method based on Green's function formalism and applied to the orbitally degenerated CB and VB to explain the calculated asymmetry. This particular asymmetry features are perfectly reproduced by advanced k. p tunneling approaches (30-band) in agreement with the Green's function methods at the first perturbation order in the SOI strength. This forward scattering asymmetry leads to skew-tunneling effects involving the branching of evanescent states waves. Recent experiments involving non-linear resistance variations vs. the transverse magnetization direction or current direction in the in-plane current geometry may invoke by the phenomenon we discuss. [Preview Abstract] |
Thursday, March 16, 2017 10:00AM - 10:12AM |
R42.00009: Spin precession and spin waves in a chiral electron gas: beyond Larmor’s theorem Shahrzad Karimi, Florent Baboux, Florent Perez, G. Karczewski, T. Wojtowicz, Carsten Ullrich Larmor's theorem holds for magnetic systems that are invariant under spin rotation. In the presence of spin-orbit coupling this invariance is lost and Larmor's theorem is broken: for systems of interacting electrons, this gives rise to a subtle interplay between the spin-orbit coupling acting on individual single-particle states and Coulomb many-body effects. We consider a quasi-two-dimensional, partially spin-polarized electron gas in a semiconductor quantum well in the presence of Rashba and Dresselhaus spin-orbit coupling. Using a linear-response approach based on time-dependent density-functional theory, we calculate the dispersions of spin-flip waves. We obtain analytic results for small wavevectors and up to second order in the Rashba and Dresselhaus coupling strengths $\alpha$ and $\beta$. Comparison with experimental data from inelastic light scattering allows us to extract $\alpha$ and $\beta$ as well as the spin-wave stiffness very accurately. We find significant deviations from the local density approximation for spin-dependent electron systems. [Preview Abstract] |
Thursday, March 16, 2017 10:12AM - 10:24AM |
R42.00010: Dispersive chiral-spin modes in a 2D Fermi-Liquid with spin-orbit coupling. Dmitrii Maslov, Saurabh Maiti Chiral-spin modes in a 2D Fermi liquid with spin-orbit coupling are oscillations of magnetization in zero magnetic field resulting from a many-body effect. We study the q-dispersion of these modes in the presence of both Rashba and Dresselahaus spin-orbit coupling and in-plane magnetic field. We show, both by symmetry arguments and explicit calculations, that the dispersion contains a leading linear in q term, which is a unique feature of spin-orbit coupling. The massive (q=0) part of the mode varies with direction of the in-plane magnetic field. These features have been observed in a series of Raman experiments in CdMnTe quantum well but were interpreted as an indication of a strong renormalization of spin-orbit coupling by electron-electron interaction. We show that the data can be explained without invoking strong renormalization effects. We also predict that these modes should be observed even in the absence of the magnetic field. [Preview Abstract] |
(Author Not Attending)
|
R42.00011: Spin-interference in complex spin-orbit fields in ring systems Henri Saarikoski, Fumiya Nagasawa, M. Wang, Junsaku Nitta We consider here interplay between complex spin-orbit (SO) and magnetic fields in spin-interference experiments in mesoscopic semiconductor ring systems. We specifically focus on Dresselhaus[001] spin-orbit interaction and Rashba spin-orbit interaction, as well as an in-plane magnetic field. In a two-dimensional (2D) electron gas subject to these SO fields weak localization effects has been predicted to give rise to anisotropic magnetoresistance as a function of in-plane field direction [A. G. Mal'shukov et al., Phys. Rev. B 59, 5702 (1999)]. However, experimental data in mesoscopic ring arrays indicates surprisingly that there is a phase shift in anisotropy as a function of spin-orbit field which is in contrast to the calculations for the 2D electron gas. We show both 1D and 2D theoretical calculations and propose that this is due to spin interference effects in the ring geometry and anisotropy from the wire is weak. We demonstrate significant 2D effects arising in multi-mode wires. [Preview Abstract] |
Thursday, March 16, 2017 10:36AM - 10:48AM |
R42.00012: Multi-orbital induced effective Rashba spin texture - the inequivalent contribution Ming-Chien Hsu, Liang-Zi Yao, Seng Ghee Tan, Mansoor B. A. Jalil, Gengchiau Liang Many important methods controlling spin in solids have been realized by Rashba effect inheriting from the interaction between spin and orbitals. However, it is usually discussed on the spin part only, while there may be increasing need to understand the role of orbitals in fields like orbitronics and spin orbit torque. Recently it was demonstrated that the orbital angular momentum texture is the basis resulting in Rashba spin texture. To better understand how various quantities influence the spin texture, the effective Rashba splitting in multi-orbital systems is re-investigated. For systems with p orbitals, two pairs of Rashba splitting with opposite signs emerge and the last one remains near degenerate, consistent with previous works. However, it is found that the amplitudes of two pairs of Rashba texture differ, not as claimed to be equal previously. This explains why usually only one significant spin splitting was observed, obscuring the discovery of orbital contributions. Both the analytical derivation and ab initio simulation show consistent results. Physical parameters like the spin-orbit coupling strength, the inversion asymmetry, and the crystal field are tuned to see how all pairs of spin texture change, demonstrating ways to control them more diversely in the future. [Preview Abstract] |
Thursday, March 16, 2017 10:48AM - 11:00AM |
R42.00013: Universality of low-energy Rashba scattering Joel Hutchinson, Joseph Maciejko In two-dimensional (2D) crystals with broken inversion symmetry, the spin degeneracy of the electronic band structure may be lifted by Rashba spin-orbit coupling. The resulting spin-split dispersion is responsible for the spin Hall effect and can also be observed in ultra-cold atoms. This spin-split dispersion is described in terms of two distinct helicity bands, but below a threshold energy, electrons are confined to one of these. At the bottom of this lower band, the density of states is enhanced to form a van Hove singularity. This is the relevant regime for a dilute spin-orbit coupled 2D electron gas, which has been shown to host a variety of exotic phases in the presence of electron-electron interactions. In this limit, electron scattering from a hard disk potential has been shown to exhibit an unusual one-dimensional characteristic in its S matrix and scattering cross-section. In this talk we show that this behaviour is universal for Rashba scattering off of any circular, finite range potential. This is relevant both for impurity scattering in the noninteracting limit as well as for short-range two-particle scattering in the interacting problem. A generic solution of the T matrix is computed, which enforces the one-dimensional character of the scattering physics. [Preview Abstract] |
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