Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X13: Hall-Bar Structure for the Detection of Spin/Valley Hall EffectInvited
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Sponsoring Units: GMAG DMP Chair: Wei Han, Peking University Room: 309 |
Friday, March 18, 2016 8:00AM - 8:36AM |
X13.00001: Topological Superconductivity in HgTe-based Devices Invited Speaker: Laurens Molenkamp Suitably structured HgTe has been shown to be a topological insulator in both 2- (a quantum well wider than some 6.3 nm) and 3 (an epilayer grown under tensile strain) dimensions with favorable properties for quantum transport studies, i.e. a good mobility and a complete absence of bulk carriers. In this talk I will summarize the results of our efforts (in collaboration with colleagues all over the globe) to induce superconductivity in the topological surface states of these materials. Special emphasis will be given to recent results on the ac Josephson effect. We will present data on Shapiro step behavior that is a very strong indication for the presence of a gapless Andreev mode in our Josephson junctions. [Preview Abstract] |
Friday, March 18, 2016 8:36AM - 9:12AM |
X13.00002: Origins of Nonlocality Near the Neutrality Point in Graphene Invited Speaker: Joshua Folk Nonlocal measurements are an effective experimental tool for probing non-charge characteristics of carriers using a (charge) transport measurement. For example, nonlocal signals in a Hall bar geometry can indicate spin currents, or valley currents, or heat currents flowing through a sample without an accompanying charge current. We present an experimental study of nonlocal electrical signals near the Dirac point in graphene, with the goal of disentangling the various types of current that might give rise to nonlocality. The in-plane magnetic field dependence of the nonlocal signal confirms the role of spin in this effect, as expected from predictions of the Zeeman spin Hall effect in graphene, but our experiments show that thermo-magneto-electric effects also contribute to nonlocality, and the effect is sometimes stronger than that due to spin. [Preview Abstract] |
Friday, March 18, 2016 9:12AM - 9:48AM |
X13.00003: Spin Hall effect and spin transport in graphene and 2D heterostructures Invited Speaker: Barbaros Oezyilmaz Semiconducting 2D materials offer new opportunities in both alternative technologies and fundamental discoveries by using the spin degree freedom of electrons. One of the main challenges in this field is to identify new materials which allow the control of spin currents by means of the electric field effect. This requires either a sizeable spin-orbit coupling strength or a sizeable bandgap or both. Unfortunately, pristine graphene has a negligibly small spin-orbit coupling strength. Recently we have addressed this problem in three distinct ways. First we have used chemical functionalization to introduce locally sp3 type bonding. Next we used metal ad-atoms to increase spin-orbit coupling via local enhancement of the spin-orbit coupling strength due to resonant scattering. Finally, I will show that the proximity of graphene on transition metal dichalcogenides can also lead to a significant enhancement of the spin-orbit coupling strength. I will complete my talk with a brief discussion on the possibility of all electrical spin injection into complementary 2D crystals such as WS2, MoS2 or black phosphorus. [Preview Abstract] |
Friday, March 18, 2016 9:48AM - 10:24AM |
X13.00004: Electron transport nonlocality in monolayer graphene modified with hydrogen silsesquioxane polymerization Invited Speaker: Alexey Kaverzin Physical properties of electrons in graphene offer not only functionality in terms of conventional charge transport, but also allow to explore spin and valley degrees of freedom. The presence of internal coupling between the nontrivial current states and normal charge current provides the effective mechanism for studying these properties. At the same time a nonlocal geometry of the transport experiments allows to separate the useful signal associated with either spin or valley degree of freedom from trivial charge contribution. In this work using the nonlocal geometry we study the transport properties of hydrogenated graphene Hall bar devices. The observed nonlocal signal is seen to substantially exceed the background ohmic contribution and, therefore, has to be understood in terms of nontrivial mediative current. The channel length dependence of the useful signal falls into direct/inverse spin Hall effect description, however, the absence of the modulation of the measured effect with the applied in plane magnetic field discredits the spin nature of the observed phenomenon. Our findings cannot be explained with the existing models suggesting that further investigation is required. [Preview Abstract] |
Friday, March 18, 2016 10:24AM - 11:00AM |
X13.00005: Spin~Hall~Angle~in~Gold~thin~films:~large~or~small? Invited Speaker: Xiaofeng Jin Most of the methods so far adopted to determine the spin~Hall~angle~are involved with the interface between a ferromagnetic (FM) and a nonmagnetic (NM) material, which would inevitably produce some complications in the analysis.~Here,~we~report~a new method~using~simply~nanoscale~H-pattern of gold, which is~free~from any interface~between~FM/NM,~to obtain~the~spin~Hall angle~in~goldthin~films.~A~spin~Hall~angle~around~0.1~is~obtained for~10nm~gold~film but negligibly small for 60 nm gold. This~result~has not~only clarified~the~controversy~about~the~spin~hall~angle in~gold~thinfilm,~but~also~proved~the~feasibility~of~using~H-pattern~to~measure~SHE~in~metallic system. [Preview Abstract] |
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