Probing Ultrafast Dynamics in EuCd₂Sb₂: Temperature and Magnetic Field Dependencies

Topological materials (TMs) have recently gained significant attention for their potential in spintronics devices and quantum computing applications which are characterized by their conductive surface states protected by time-reversal symmetry. These gapless surface states emerge from band inversion and the influence of spin-orbit coupling. Here, we present our work on the ultrafast carrier dynamics in single crystals of the topological material EuCd₂Sb₂, achieved through the utilization of a two-color optical pump-optical probe (OP-OP) technique. The time-domain traces of transient reflectivity (ΔR/R) of the probe pulses were recorded in the temperature range of 2-300 K. In addition, we also applied different magnetic fields (1, 2, 3, 4, 5, and 6 T) parallel to c-axis of the sample and performed the OP-OP measurements in the temperature range of 2-300 K. The significant observations from the OP-OP measurements include, (i) transition from positive ΔR/R signal to a negative ΔR/R signal at around 120 K, (ii) appearance of a slow frequency mode of 0.03 THz at all temperatures and fields, and (iii) origin of a new frequency mode at 0.16 THz after application of 6 T. The detailed analysis of these results will be carried out to have a deeper understanding on the ultrafast dynamics of EuCd₂Sb₂ single crystals. Further, we will also carry out a detailed magnetic measurements using superconducting quantum interference devices to elucidate the magnetic phase transitions