Stacking effects on magnetic, vibrational, and optical properties of CrSBr bilayers

Layer stacking presents a promising avenue for manipulating the physical properties of two-dimensional materials. The van der Waals layered semiconductor CrSBr, which exhibits A-type antiferromagnetism and a relatively high N\'eel temperature, has been successfully exfoliated into atomically thin sheets. In this paper, we investigate the structural, lattice dynamical, electronic, magnetic, and optical properties of four distinct stacking structures of CrSBr bilayers using first-principles calculations and Monte Carlo simulations. Our findings show that, though the most energetically favorable bilayer structure retains the stacking pattern of the bulk counterpart, three other high-symmetry stacking structures can be achieved by sliding one of the layers along three distinct directions, with energy cost comparable to that observed in ${\mathrm{MoS}}_{2}$ bilayer. All these four bilayers exhibit semiconductor behavior with A-type antiferromagnetic ordering, similar to the bulk material, and demonstrate closely aligned N\'eel temperatures. Moreover, these bilayers exhibit relatively low lattice thermal conductivities, pronounced anisotropy, and a strong dependence on stacking patterns. This behavior is attributed to significant phonon-phonon scattering arising from avoided crossings between acoustic and optical phonons, as well as the presence of flat optical phonon bands in the low-frequency region. While the electronic structures and optical properties of these bilayers show weak dependence on the stacking pattern for antiferromagnetic ordering, they undergo significant changes for ferromagnetic ordering, influencing the band gap, valence and conduction band splitting, and effective mass. Furthermore, we found that antiferromagnetic ordering can transition to ferromagnetic under intense light illumination. Thus, the integration of layer stacking and light illumination offers an effective means to control the heat transfer, magnetic, and optical properties of CrSBr bilayers.