Ultrafast electron transport in metallic antiferromagnetic Mn2Au thin films probed by terahertz spectroscopy

The ultrafast electron transport is central to the requirement of all-electrically controlled spintronics in metallic collinear antiferromagnetic (AFM) ${\mathrm{Mn}}₂\mathrm{Au}$ thin films within the terahertz (THz) range. Here we use the THz time-domain spectroscopy to measure the conductivity spectra of ${\mathrm{Mn}}₂\mathrm{Au}$ thin films with different thicknesses and temperatures. We demonstrate an onset of carrier localization in ${\mathrm{Mn}}₂\mathrm{Au}$ with decreasing the film thickness from 15 to 5 nm. By using optical pump-THz probe spectroscopy, we found the surface trapping states in the thinnest ${\mathrm{Mn}}₂\mathrm{Au}$ film limit its photoconductivity significantly. The DC conductivity and scattering time become larger and longer with decreasing temperature for all samples, which suggests that ${\mathrm{Mn}}₂\mathrm{Au}$ behaves in a typical metallic fashion. The THz optical and conductivity properties of ${\mathrm{Mn}}₂\mathrm{Au}$ films will advance our understanding of ultrafast electronic transport processes in AFM ${\mathrm{Mn}}₂\mathrm{Au}$ thin films.