Quasi 1D electronic transport in a 2D magnetic semiconductor

TL;DR

This study reveals that multilayer CrSBr exhibits quasi-1D electronic transport behavior, characterized by strong anisotropy and unconventional transport signatures, challenging the traditional 2D band transport model.

Contribution

It demonstrates that CrSBr's electronic transport is better described as weakly coupled 1D wires, marking the first observation of quasi-1D transport in a 2D semiconductor.

Findings

Pronounced anisotropy in conductivity along crystallographic directions

Observation of a 1D van Hove singularity in photocurrent measurements

Transport behavior inconsistent with conventional 2D band theory

Abstract

We investigate electronic transport through exfoliated multilayers of CrSBr, a 2D semiconductor that is attracting attention because of its magnetic properties. We find an extremely pronounced anisotropy that manifests itself in qualitative and quantitative differences of all quantities measured along the in-plane \textit{a} and \textit{b} crystallographic directions. In particular, we observe a qualitatively different dependence of the conductivities $\sigma_a$ and $\sigma_b$ on temperature and gate voltage, accompanied by orders of magnitude differences in their values ($\sigma_b$/$\sigma_a \approx 3\cdot10^2-10^5$ at low temperature and large negative gate voltage). We also find a different behavior of the longitudinal magnetoresistance in the two directions, and the complete absence of the Hall effect in transverse resistance measurements. These observations appear not to be compatible with a description in terms of conventional band transport of a 2D doped semiconductor. The observed phenomenology -- together with unambiguous signatures of a 1D van Hove singularity that we detect in energy resolved photocurrent measurements -- indicate that electronic transport through CrSBr multilayers is better interpreted by considering the system as formed by weakly and incoherently coupled 1D wires, than by conventional 2D band transport. We conclude that CrSBr is the first 2D semiconductor to show distinctly quasi 1D electronic transport properties.