Giant Transport Anisotropy in ReS$_2$ Revealed via Nanoscale Conducting Path Control

TL;DR

This study demonstrates giant transport anisotropy in ReS$_2$ by controlling nanoscale conducting paths with ferroelectric polarization, revealing extreme directional conductivity differences and underlying band structure origins.

Contribution

It introduces a method to control and measure giant anisotropic transport in ReS$_2$ using ferroelectric polarization, uncovering the band origin of the anisotropy.

Findings

Conductivity switching ratio >1.5x10^8 at 300 K.

Conductivity anisotropy ratio exceeds 5.5x10^4.

Emergence of a flat band in few-layer ReS$_2$.

Abstract

The low in-plane symmetry in layered 1T'-ReS$_2$ results in strong band anisotropy, while its manifestation in the electronic properties is challenging to resolve due to the lack of effective approaches for controlling the local current path. In this work, we reveal the giant transport anisotropy in monolayer to four-layer ReS$_2$ by creating directional conducting paths via nanoscale ferroelectric control. By reversing the polarization of a ferroelectric polymer top layer, we induce conductivity switching ratio of >1.5x10$^8$ in the ReS$_2$ channel at 300 K. Characterizing the domain-defined conducting nanowires in an insulating background shows that the conductivity ratio between the directions along and perpendicular to the Re-chain can exceed 5.5x10$^4$. Theoretical modeling points to the band origin of the transport anomaly, and further reveals the emergence of a flat band in few-layer ReS$_2$. Our work paves the path for implementing the highly anisotropic 2D materials for designing novel collective phenomena and electron lensing applications.