Electric modulation of the Fermi arc spin polarization of a Dirac semimetal nanowire

The spin polarization of the exotic topological surface states of Dirac/Weyl semimetals, namely Fermi arcs, were predicted to exist but never accessed in a simple transport structure. Here we report the direct access of the Fermi arc spin polarization through the electromagnetic transport experiment. The net spin polarization was manifested as a voltage of the ferromagnetic contact, which was induced by applying a charge current via spin momentum locking property of the Fermi arc in the Cd₃As₂ nanowire. Moreover, a gate voltage controlled topological phase transition of the surface states is demonstrated to be able to switch on/off the spin signals. Thus a topological field-effect transistor is proposed.