Research & Reviews: Journal of Material Sciences
MenuISSN:2321-6212
ISSN:2321-6212
Jia G Lu
University of Southern California, USA
Posters & Accepted Abstracts: Res. Rev. J Mat. Sci
The momentum and spin of charge carriers in the topological insulators are constrained to be perpendicular due to strong spin-orbit coupling. Sb2Te3 is one of the topological insulator materials with a bulk band gap of 0.28 eV and simple surface states consisting of a single Dirac cone in the band gap. We have synthesized single crystalline Sb2Te3 nanowires using low pressure catalytic chemical vapor deposition, via vapor-liquid-solid growth mechanism. Two levels of aligned e-beam lithography were used to pattern non-magnetic outer Au leads and two magnetic tunnel junction inner leads on individual Sb2Te3 nanowires. The tunnel junction leads consist of a free Py (Ni80Fe20) layer, whose magnetization determines the magnitude and direction of spin current injected into the Sb2Te3 nanowire. Measurements of the device resistance between the two Au leads reveal that the Au/Sb2Te3 contact is ohmic. The two-point resistance measured between these contacts as a function of magnetic field shown exhibits positive magneto-resistance, originating from weak anti-localization of carriers in the Sb2Te3 nanowire induced by spin-orbit interaction. The weak anti-localization signal serves as evidence of a strong impact of spin orbit interaction on transport in the Sb2Te3 nanowire system. We have also measured a non-local spin valve signal in Sb2Te3 nanowire channels. The symmetry of this non-local spin valve (NLSV) signal is dramatically different from that of an NLSV with a channel that lacks spin-momentum locking (such as graphene). Two parallel states of the injector and detector magnetic moments give rise to different non -local voltage values, which is never observed in conventional NLSVs. This unusual symmetry is a clear signature of the spin-momentum locking in the Sb2Te3nanowire surface state.
E-mail:
jialu@usc.edu