Quasiparticle and Spin Dynamics in MnBi2Te4 using time-resolved magneto-optical Kerr spectroscopy.

Using ultrafast optical spectroscopy, we have investigated quasiparticle and spin dynamics in MnBi₂Te₄, an intrinsic magnetic topological insulator that exhibits A-type anti-ferromagnetism at T_N=24K. The dynamics were measured as a function of temperature and magnetic field using femtosecond optical-pump, near-IR measurements of the reflectivity and magneto-optical Kerr effect (MOKE). The time-resolved MOKE measurements reveal coherent spin precession (~7GHz) in the canted AFM phase which softens with increasing fluence or increasing temperature. In this presentation, we will delineate the field, fluence, and temperature dependence of the long time dynamics in this enigmatic antiferromagnetic topological insulator.