Localisation-to-delocalisation transition of moir\'e excitons in WSe2/MoSe2 heterostructures
Abstract
Moir\'e excitons (MXs) are electron-hole pairs localised by the periodic (moir\'e) potential forming in two-dimensional heterostructures (HSs). MXs can be exploited, e.g., for creating nanoscale-ordered quantum emitters and achieving or probing strongly correlated electronic phases at relatively high temperatures. Here, we studied the exciton properties of a WSe2/MoSe2 HS from T=6 K to room temperature using time-resolved and continuous-wave micro-photoluminescence, also under magnetic field. The exciton dynamics and emission lineshape evolution with temperature show clear signatures that MXs de-trap from the moir\'e potential and turn into free interlayer excitons (IXs) at T120 K. The MX-to-IX transition is also apparent from the exciton magnetic moment reversing its sign when the moir\'e potential is not capable to localise excitons at elevated temperatures. Concomitantly, the exciton formation and decay times reduce drastically. Thus, our findings establish the conditions for a truly confined nature of the exciton states in a moir\'e superlattice with increasing temperature.
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