Strain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenides

The spin-valley physics of monolayer transition metal dichalcogenides (TMDs) remains one of the main interests in the class of van der Waals materials. At low temperature, it is mainly driven by the electron-hole exchange interaction (EHEI) that describes the annihilation of an exciton in one valley and the creation of an exciton in the time-reversal equivalent valley. Here, the authors show that the EHEI in monolayer TMDs is biaxial strain dependent and, surprisingly, it is an order of magnitude more strain dependent than expected from these first principles calculations. This points to a valley scattering channel that has not been considered in the literature so far.