Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session B6: Spin Relaxation and Spin Orbit |
Hide Abstracts |
Chair: Cheng Cen, West Virginia University Room: Waterfront Hotel Salon F |
Saturday, October 24, 2015 3:30PM - 4:06PM |
B6.00001: Spin relaxation via exchange with donor impurity-bound electrons Invited Speaker: Ian Appelbaum At low temperatures, electrons in semiconductors are bound to shallow donor impurity ions, neutralizing their charge in equilibrium. Inelastic scattering of other externally injected conduction electrons accelerated by electric fields can excite transitions within the manifold of these localized states. Promotion of the bound electron into highly spin-orbit-mixed excited states drives a strong spin relaxation of the conduction electrons via exchange interactions, reminiscent of the Bir-Aronov-Pikus process where exchange occurs with valence band hole states. Through low-temperature experiments with silicon spin transport devices and complementary theory, we reveal the consequences of this spin depolarization mechanism both below and above the impact ionization threshold. [Preview Abstract] |
Saturday, October 24, 2015 4:06PM - 4:18PM |
B6.00002: Optical helicity control of surface current in SmB$_{\mathrm{6}}$ Sanjay Adhikari, Yanjun Ma, Chang-Beom Eom, Cheng Cen SmB$_{\mathrm{6}}$ is a promising candidate for topological Kondo insulator. Transport measurements and spin resolved ARPES measurements have indicated signatures of topologically protected surface states. One hallmark signature of such states is the helical Dirac dispersion with perfect momentum-spin lockage. Here, we report current injection in SmB6 thin film with circularly polarized light at oblique incidence. A polarization-independent photovoltage was also detected. Both signals exhibited strong temperature dependences. While the polarization-independent photovoltage is likely due to thermoelectric or photovoltaic effects, the circular photogalvanic effect also has two possible origins: topological surface states or regular surface states with strong Rashba type spin-orbit coupling. To shed more light onto the nature of the surface states observed in SmB6, experiments were performed on thin films with different capping layers. This research enhances our knowledge in controlling the spin and orbital degrees of freedom at SmB$_{\mathrm{6}}$ surface, and can lead to exciting spintronic applications using optical tools. [Preview Abstract] |
Saturday, October 24, 2015 4:18PM - 4:30PM |
B6.00003: Polarization dependent photocurrent in topological insulators tuned by an in plane magnetic field Yu Pan, Timothy Pillsbury, Brittany Grimm, Anthony Richardella, Thomas Flanagan, Nitin Samarth Illumination with circularly polarized light is known to produce a helicity dependent photocurrent in topological insulators such as Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ \begin{figure}[htbp] \centerline{\includegraphics[width=0.43in,height=0.17in]{280920151.eps}} \label{fig1} \end{figure} [Nature Nanotech. \textbf{7}, 96 (2012)]. Symmetry considerations suggest that this ``circular photo-galvanic effect'' (CPGE) arises purely from the surface. However, whether or not the CPGE is directly related to optical excitations from the helical surface states is still under debate. Since the helical surface states of a 3D topological insulator are not greatly perturbed by a static in-plane magnetic field, the response of the CPGE to an in-plane magnetic field could help elucidate the origin of the CPGE. We report photocurrent measurements in Al capped (Bi, Sb)$_{\mathrm{2}}$Te$_{\mathrm{3}}$ \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.17in]{280920152.eps}} \label{fig2} \end{figure} thin films as an in-plane magnetic field is applied. The polarization dependent photocurrent is greatly enhanced by the in-plane magnetic field, reversing sign as the field switches direction. Further, we find that field-dependence of the photocurrent is much weaker in similar (Bi, Sb)$_{\mathrm{2}}$Te$_{\mathrm{3}}$ \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.17in]{280920153.eps}} \label{fig3} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.17in]{280920154.eps}} \label{fig4} \end{figure} films without Al capping. Control measurements on Al capped n-Si rule out a field-dependent CPGE that originates in the Al overlayer. We thus attribute the field-dependent photocurrent to the interface between the Al and (Bi, Sb)$_{\mathrm{2}}$Te$_{\mathrm{3}}$ \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.17in]{280920155.eps}} \label{fig5} \end{figure} \begin{figure}[htbp] \centerline{\includegraphics[width=0.78in,height=0.17in]{280920156.eps}} \label{fig6} \end{figure} thin film. This work is supported by ONR. [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