Enhancement in optically induced ultrafast THz response of MoSe2MoS2 heterobilayer

THz conductivity of large area MoS2 and MoSe2 monolayers as well as their vertical heterostructure, MoSe2MoS2 is measured in the 0.3-5 THz frequency range. Compared to the monolayers, the ultrafast THz reflectivity of the MoSe2MoS2 heterobilayer is enhanced many folds when optically excited above the direct band gap energies of the constituting monolayers. The free carriers generated in the heterobilayer evolve with the characteristic times found in each of the two monolayers. Surprisingly, the same enhancement is recorded in the ultrafst THz reflectivity of the heterobilayer when excited below the MoS2 bandgap energy. A mechanism accounting for these observations is proposed. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The THz conductivity of large area MoS2 and MoSe2 monolayers and their vertical heterostructure, MoSe2MoS2, was measured in the 0.3-5 THz frequency range. The ultrafast THz reflectivity of the MoSe2MoS2 heterobilayer is greatly enhanced when optically excited above the direct band gap energies of the constituting monolayers, with free carriers evolving with characteristic times found in each monolayer. Surprisingly, a similar enhancement is observed in the ultrafast THz reflectivity of the heterobilayer when excited below the bandgap energy of MoS2, with a proposed mechanism to explain these observations.