Ultrafast dynamics of photoexcited carriers in tellurium in the vicinity of Weyl nodes

The authors study here the ultrafast dynamics of photoexcited carriers in the Weyl semiconductor Te in the vicinity of Weyl nodes using mid-infrared transient reflection spectroscopy. The relaxation process in a 20-nm Te flake is found to be 10 times faster than a 100-nm flake due to surface defect assisted recombination. The reflection modulation depth of the 20-nm sample is up to 60%, promising great potential for fast optical switch and optical modulator applications in the mid-infrared region.