Giant exchange splitting in the electronic structure of A-type 2D antiferromagnet CrSBr

Abstract We present the evolution of the electronic structure of CrSBr from its antiferromagnetic ground state to the paramagnetic phase above T N = 132 K, in both experiment and theory. Low-temperature angle-resolved photoemission spectroscopy (ARPES) results are obtained using a novel method to overcome sample charging issues, revealing quasi-2D valence bands in the ground state. The results are very well reproduced by our $${\rm{QSG}}\hat{{\rm{W}}}$$ QSG W ̂ calculations, which further identify certain bands at the X points to be exchange-split pairs of states with mainly Br and S character. By tracing band positions as a function of temperature, we show the splitting disappears above T N . The energy splitting is interpreted as an effective exchange splitting in individual layers in which the Cr moments all align, within the so-called A-type antiferromagnetic arrangement. Our results lay firm foundations for the interpretation of the many other intriguing physical and optical properties of CrSBr.