Influence of carrier localization on terahertz conductivity in Weyl semimetal Mn3Sn thin films

The topological semimetal Mn3Sn, known for its strong electronic correlation characteristics, is of significant importance for research into its optoelectronic properties within the terahertz (THz) frequency spectrum. Here, we systematically investigate THz response of nearly continuous and granular Mn3Sn by THz time-domain spectroscopy from 1.5 to 300 K. The results indicate that the THz response can be greatly modulated by the morphology of sample due to carrier localization. For nearly continuous samples, the transition from semiconductor to metal can be observed as the temperature increases, and the THz conductivity can be described by the Drude model within the range of 0.2–1 THz. For granular samples, the real part of the THz conductivity is an order of magnitude smaller than that of nearly continuous ones, and it exhibits temperature insensitivity and a negative imaginary part of THz conductivity. Moreover, we have observed two absorption peaks induced by localized surface plasmon resonance (LSPR) at ∼1.2 and ∼1.7 THz. The findings not only enhance our understanding of the photoelectric properties of Mn3Sn thin films but also pave the way for studying the THz conductivity of thin films.