Interlayer-Exciton Based Nonvolatile Valleytronic Memory

Abstract Analogous to conventional charge-based electronics, valleytronics aims at encoding data via valley degree of freedom, enabling new routes for information processing. Long-lived interlayer excitons (IXs) in van der Waals heterostructures (HSs) stacked by transition metal dichalcogenides (TMDs) carry valley-polarized information and thus would find promising applications in valleytronic devices. Although great progress of IX based valleytronic devices has been achieved, nonvolatile valleytronic memories are still challenging. Here, we demonstrate IX based nonvolatile valleytronic memory in a WS2/WSe2 HS. The emission characteristics of IX exhibit a large excitonic/valleytronic hysteresis upon cyclic-voltage sweeping. Importantly, IX emission can be electrically switched between a bright state and a dark state with large light-intensity and helicity contrast of about 1.7 and 1.8, respectively, which can be ascribed to the chemical-doping of O2/H2O redox couple between TMDs and substrate. Taking advantage of the large hysteresis, IX can be utilized for manipulating and nonvolatile storing valley information and IX based nonvolatile valleytronic memory has been successfully demonstrated. These findings open up an avenue for nonvolatile valleytronic memory and would motivate more investigations on valleytronic devices.