Optical Conductivity and Photo‐Induced Polaronic Formation in Co₂MnGa Topological Semimetal

Abstract

Topological materials occupy an important place in the quantum materials family due to their peculiar low‐energy electrodynamics, hosting emergent magneto‐electrical, and nonlinear optical responses. This manuscript reports on the optical responses for the magnetic topological nodal semimetal Co2MnGa, studied in a thin film geometry at various thicknesses. The thickness‐dependent optical conductivity is investigated, observing a substantial dependence of the electronic band structure on thickness. Additionally, details on the ultrafast response of the low energy excitations in the terahertz frequency are reported by employing optical pump‐terahertz probe (OPTP) spectroscopy. In particular, the photocarrier dynamics of Co2MnGa thin films is studied at varying pump fluence, pump wavelength, and film thickness, observing a negative THz photoconductivity which is assigned to a dynamical formation of large polarons in the material.