Evidence of the ferroelectric polarization in charge transport through WTe2 Weyl semimetal surface
N. N. Orlova, N. S. Ryshkov, A. V. Timonina, N. N. Kolesnikov, E. V. Deviatov
Institute of Solid State Physics of the Russian Academy of Sciences, 142432 Chernogolovka, Russia
We investigate electron transport along the surface of WTe2 three-dimensional
single crystals, which are characterized by the coexistence of Weyl semimetal
conductivity and ferroelectricity at room temperature. We find that non-linear
behavior of dV/dI(I) WTe2 differential resistance is accompanied by slow
relaxation process, which appears as the dV/dI(I) dependence on the sign of
the current change. This observation is confirmed by direct investigation of
time-dependent relaxation curves. While strongly non-linear differential
resistance should be expected for the zero-gap WTe2, the slow relaxation in
transport is very unusual for well-conducting semimetals at room temperature.
We establish, that non-monotonic dependence of the amplitude of the effect on
driving current Δ dV/dI(I) well corresponds to the known Sawyer-Tower's
ferroelectric hysteresis loop. The possibility to induce polarization current
by source-drain field variation is unique for WTe2, since it is a direct
consequence of the coexistence of ferroelectricity and metallic conduction.
This conclusion is also confirmed by gate voltage dependencies, so our results
can be understood as a direct demonstration of WTe2 ferroelectric behavior in
charge transport experiment.