Ultrafast dynamics of optically excited charge carriers in the room-temperature antiferromagnetic semiconductor α-MnTe

We report on time-resolved optical and terahertz ultrafast spectroscopy of charge-carrier dynamics in the room-temperature antiferromagnetic semiconductor α-MnTe. By optically pumping the system with 1.55 eV photons at room temperature, we excite charge carriers in the conduction band through the indirect band gap and investigate the dynamical response of the nonequilibrium states using optical as well as terahertz transmission probes. Three relaxation processes are revealed by their characteristic relaxation times of the order of 1, 10, and 100 ps, whose exact values are a function of the pump fluence. For high pump fluences a nonlinear dependence on the pump fluence is observed both in the optical and terahertz probes.