The Bulk van der Waals Layered Magnet CrSBr is a Quasi-1D Material

Abstract

Correlated quantum phenomena in one-dimensional (1D) systems that exhibit competing electronic and magnetic order are of strong interest for the study of 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 for 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 X e/m Y e ∼ 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 to that of metallic carbon nanotubes. Moreover, because of 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.

Optical markers of magnetic phase transition in CrSBr

“…Such an exciton can inherit the 1D character and show pronounced exciton-phonon coupling effects. 28 The temperature dependence of the optical transition of CrSBr has also been comprehensively investigated. For this purpose PR and absorption measurements have been performed in the temperature range from 20 to 300 K. Fig.…”

“…Such an exciton can inherit the 1D character and show pronounced exciton–phonon coupling effects. 28…”

Ferromagnetic Interlayer Coupling in CrSBr Crystals Irradiated by Ions

“…Due to the pronounced correlations between magnons, photons, electrons, and phonons, ,− CrSBr is emerging as one of the most promising materials for such applications. Up to the Néel temperature of T N = 132 ± 1 K, the FM spin order within each layer is compensated by an AFM arrangement of the vdW layers in the out-of-plane direction ( c -axis), which is the reason for the vanishing net magnetization of pristine bulk crystals.…”

Charge Transfer and Asymmetric Coupling of MoSe2 Valleys to the Magnetic Order of CrSBr

“…The electronic band structure, and consequently the energy of excitons in CrSBr, are sensitive to the interlayer magnetic exchange interaction which can be used to probe its magnetic properties. 7,28,30,34 Monolayer MoSe 2 is a direct band gap semiconductor with two inequivalent ±K valleys and robust excitons. 35−43 Under out-of-plane magnetic fields, valley Zeeman effects and magnetic-field-induced valley polarization are observed, and these effects depend on the presence of strain, doping, and magnetic proximity effects.…”