The two conduction bands of monolayer CrSBr on Au

Angle-resolved photoemission spectroscopy (ARPES) measurements on insulating materials are a challenge due to sample charging, however using thin flakes exfoliated onto gold mitigates this, allowing high resolution and low temperature measurements. Further, in the case that the flake is monolayer thickness, and the gold is ultraflat due to the template-stripping preparation, novel charge transfer and hybridisation effects can be encountered. Here we focus on the electronic structure of monolayer CrSBr - a 2D magnetic material - exfoliated onto mica template-stripped gold substrates. ARPES reveals charge transfer from the substrate, populating the conduction band of monolayer CrSBr, accompanied by a pronounced reduction in the quasiparticle band gap. Furthermore, we observe two separate conduction bands that exhibit a splitting at the X point. This indicates a breaking of glide-mirror symmetry, which in the bulk or in a free-standing monolayer protects the band degeneracies at the Brillouin zone boundary. Our results demonstrate that ultraflat gold substrates do more than modify carrier densities and screening: they can lift symmetry-protected degeneracies and thus fundamentally reshape the band topology of 2D materials.

https://arxiv.org/abs/2510.04925