Current-induced control of the polarization state in a polar metal based heterostructure SnSe/WTe$_2$

Abstract

The concept of a polar metal proposes new approach of current-induced polarization control for ferroelectrics. We fabricate SnSe/WTe2 heterostructure to experimentally investigate charge transport between two ferroelectric van der Waals materials with different polarization directions. WTe2 is a polar metal with out-of-plane ferroelectric polarization, while SnSe ferroelectric semiconductor is polarized in-plane, so one should expect complicated polarization structure at the SnSe/WTe2 interface. We study dI/dV (V ) curves, which demonstrate sharp symmetric drop to zero dI/dV differential conductance at some threshold bias voltages ±V th , which are nearly symmetric in respect to the bias sign. While the gate electric field is too small to noticeably affect the carrier concentration, the positive and negative threshold positions are sensitive to the gate voltage. Also, SnSe/WTe2 heterostructure shows re-entrant transition to the low-conductive dI/dV = 0 state for abrupt change of the bias voltage even below the threshold values. This behavior can not be observed for single SnSe or WTe2 flakes, so we interpret it as a result of the SnSe/WTe2 interface coupling. In this case, some threshold value of the electric field at the SnSe/WTe2 interface is enough to drive 90 • change of the initial SnSe in-plane polarization in the overlap region. The polarization mismatch leads to the significant interface resistance contribution, analogously to the scattering of the charge carriers on the domain walls. Thus, we demonstrate polarization state control by electron transport through the SnSe/WTe2 interface.