Magneto-photoconductivitity of atomically thin transition metal dichalcogenides

Photoinduced effects of two-dimensional (2D) transition metal dichalcogenides (TMDs) are of great interest since the bandgap of these materials corresponds to visible range of spectrum. For instance, in molybdenum disulphide (MoS$_{2})$ -- a 2D semiconductor TMD and a non-centrosymmertic crystal, inherent broken inversion symmetry in monolayers leads to a large spin-orbit interaction which splits the valence band (VB) by 160 meV and gives rise to strong excitonic transitions due to the direct band gap at low energy \textbf{\textit{K}} and \textbf{\textit{--K}} valleys. The same broken inversion symmetry together with time reversal symmetry is responsible for spin-valley coupling in monolayer MoS$_{2}$ and similar TMDs (such as tungsten disulphide, WS$_{2})$. Spin-valley coupled band edges in TMDs result in different localization behaviors for different scattering mechanisms. In this work, we present our magneto-photoconductivity studies of mono- and bilayer field-effect transistor devices of MoS$_{2}$ and WS$_{2}$, and discuss our results in terms of localization effects.