Excitons in the Layered Magnetic Semiconductor CrSBr

Materials with a correlated degree of spin, lattice, and charge are attractive platforms for the study of fundamental magneto-correlated phenomena and for realizing spin-based devices for spintronic applications. Such physics was initially explored in dilute magnetic semiconductors; however, their structural inhomogeneity limited their study. Fortunately, such ideas transfer to the emerging class of layered magnetic semiconductors with chromium sulfide bromide (CrSBr) as a prime candidate for such explorations. Unlike dilute systems, materials such as CrSBr are structurally homogenous and benefit from the well-known property enhancements that layered materials exhibit. In this unique combination, new opportunities arise for the study of a breadth of quasiparticle excitations immersed in magnetic environments.<br/>In my talk, I will elaborate on the rich excitonic physics of CrSBr and showcase new opportunities for its control. I will start by showing that CrSBr is a quasi-1D material. The extreme anisotropy is manifested in its excitons, electronic band structure, a Peierls-like structural instability, and strong exciton-phonon and electron-phonon interactions. [1] As such, CrSBr is best rationalized as a stack of weakly coupled monolayers, each hosting tightly bound quasi-1D excitons. Second, I will discuss the crystal defects in CrSBr and provide a link to their optical emission properties. In particular, I will discuss the correlation of defects with a defect-magnetic order. [2] Lastly, I will demonstrate that CrSBr is an exceptional material for the controlled generation of crystal defects using a focused electron beam. [3] I will provide an outlook and motivate this as a key ingredient for controlling quasiparticle excitations and magneto-correlated phenomena one atom at a time.<br/><br/>References<br/>[1] J. Klein et al., <i>ACS Nano <b>17</b>, 5316–5328</i> (2023)<br/>[2] J. Klein et al., <i>ACS Nano</i> <b><i>17</i></b><i>, 288–299</i> (2023)<br/>[3] J. Klein et al., <i>Nat. Comms. <b>13</b>, 5420</i> (2022)