Current-induced control of the polarization state in a polar-metal–based heterostructure SnSe/WTe2

Abstract

Abstract The concept of a polar metal suggests a new approach to 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 curves, which demonstrate sharp symmetric drop to zero differential conductance at some threshold bias voltages , which are nearly symmetric with 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 state for abrupt change of the bias voltage even below the threshold values. This behavior cannot 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 a 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.