  Circular photogalvanic currents are a promising new approach for
spin-optoelectronics. To date, such currents have only been induced in
topological insulator flakes or extended films. It is not clear whether they
can be generated in nanodevices. In this paper, we demonstrate the generation
of circular photogalvanic currents in $\text{Bi}_2\text{Se}_3$ nanowires. Each
nanowire shows topological surface states. Here, we generate and distinguish
the different photocurrent contributions via the driving light wave. We
separate the circular photogalvanic currents from those due to thermal Seebeck
effects, through controlling the laser light polarization. The results reveal a
spin-polarized surface-Dirac electron flow in the nanowires arising from
spin-momentum locking and spin-orbit effects. The second photocurrent
contribution described in this letter is caused by the thermal Seebeck effect.
By scanning the photocurrent, it can be spatially resolved; upon reversing the
gradient direction along the nanowire, the photocurrent changes its sign, and
close to the gold contacts, the amplitudes of the different photocurrent
contributions are affected by the proximity to the contacts. In the center of
the nanowires, where the effects from the gold contact/ topological insulator
stacks vanish, the spin-polarized current remains constant along the nanowires.
This opens up a new method of all-optical spin current generation in
topological insulator nanowires and hybrid structures for nanoscale
spin-orbitronics.
