The bulk van der Waals layered magnet CrSBr is a quasi-1D material

TL;DR

CrSBr is a van der Waals layered magnetic semiconductor that exhibits quasi-one-dimensional electronic behavior, leading to strong anisotropic interactions, narrow excitons, and potential for studying 1D correlated physics with magnetic order.

Contribution

This work demonstrates that CrSBr behaves as a quasi-1D material with extreme anisotropy, revealing novel electronic and excitonic properties in a magnetic layered system.

Findings

CrSBr exhibits strong electronic anisotropy with an effective mass ratio of ~50.

CrSBr hosts narrow excitons (~1 meV) with high binding energy and oscillator strength.

CrSBr shows Peierls-like instability and Fano resonance due to van Hove singularity.

Abstract

Correlated quantum phenomena in one-dimensional (1D) systems that exhibit competing electronic and magnetic order are of strong interest for studying fundamental interactions and excitations, such as Tomonaga-Luttinger liquids and topological orders and defects with properties completely different from the quasiparticles expected in their higher-dimensional counterparts. However, clean 1D electronic systems are difficult to realize experimentally, particularly magnetically ordered systems. Here, we show that the van der Waals layered magnetic semiconductor CrSBr behaves like a quasi-1D material embedded in a magnetically ordered environment. The strong 1D electronic character originates from the Cr-S chains and the combination of weak interlayer hybridization and anisotropy in effective mass and dielectric screening with an effective electron mass ratio of $m^e_X/m^e_Y \sim 50$. This extreme anisotropy experimentally manifests in strong electron-phonon and exciton-phonon interactions, a Peierls-like structural instability and a Fano resonance from a van Hove singularity of similar strength of metallic carbon nanotubes. Moreover, due to the reduced dimensionality and interlayer coupling, CrSBr hosts spectrally narrow (1 meV) excitons of high binding energy and oscillator strength that inherit the 1D character. Overall, CrSBr is best understood as a stack of weakly hybridized monolayers and appears to be an experimentally attractive candidate for the study of exotic exciton and 1D correlated many-body physics in the presence of magnetic order.