Nina Meyer
Topological Insulators (TI) open up a new route to influence the transport of charge and spin via spin-momentum locking [1,2]. It has been demonstrated experimentally [2] that spin-polarized surface currents can be generated and controlled by illuminating a TIwithcircularly polarizedlight.In this talk,we will present the experimental results onphotocurrent measurements on(Bi,Sb)2Te3thin filmHall bar devicesand on Bi2Se3and Bi2Te3nanowire devices. We generate and distinguish the different photocurrent contributionsby controlling the polarization of the driving light wave, focusing on the polarization independent term whichis related to theSeebeck effect and the helicity dependentterm whichwe relate to the circular photogalvanic effect.Moving the laser spot across the sample surface and analyzing the measured photocurrentspatially resolved at every laser spot position enables us to display and discuss the thermoelectric and spin-polarized current as two-dimensionalmaps. For the (Bi,Sb)2Te3Hall bar deviceswe see a lateral accumulation of spin-polarizedcurrent at the TI’s edgeswhichin combination with the thermalgradient along the Hall bar can be explainedby the spin Nernst effect [3]. For the nanowire devices,the findings depend on the region of the sample.When the laser spot illuminates the layer stack of the contact and the nanowire the thermoelectric and the spin-polarized current are enhancedand the sign of spin-polarized current differs at the contact edges. Where the gold contacts of the nanowire are negligible we detect a constant spin polarized current along the nanowirewhich shows their promising potential for optospintronic applications [4].
We acknowledge funding through DFG priority program SPP "Topological Insulators" and DAAD PPP Czech Republic "FemtomagTopo".
[2] J.W. McIver et al., Nature Nanotechnology 7, 96-100 (2012)
[3] T. Schumann et al., arXiv:1810.12799
[4] N. Meyer et al., Appl. Phys. Lett. 116, 172402 (2020)