Abstract
Long-lived interlayer excitons (IXs) in van der Waals heterostructures (HSs) stacked by monolayer transition metal dichalcogenides (TMDs) carry valley-polarized information and thus could find promising applications in valleytronic devices. Current manipulation approaches for valley polarization of IXs are mainly limited in electrical field/doping, magnetic field or twist-angle engineering. Here, we demonstrate an electrochemical-doping method, which is efficient, in-situ and nonvolatile. We find the emission characteristics of IXs in WS2/WSe2 HSs exhibit a large excitonic/valley-polarized hysteresis upon cyclic-voltage sweeping, which is ascribed to the chemical-doping of O2/H2O redox couple trapped between WSe2 and substrate. Taking advantage of the large hysteresis, a nonvolatile valley-addressable memory is successfully demonstrated. The valley-polarized information can be non-volatilely switched by electrical gating with retention time exceeding 60 min. These findings open up an avenue for nonvolatile valley-addressable memory and could stimulate more investigations on valleytronic devices.
Highlights
IntroductionIntroduction Van derWaals heterostructures (HSs) stacked by transition metal dichalcogenides (TMDs) monolayers enable the generation of long-lived interlayer excitons (IXs) with a large binding energy of about 150 meV1 and a long diffusion distance over five micrometers[2], further extending the already appealing properties of the constituent TMDs monolayers
1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; Introduction Van der Waals heterostructures (HSs) stacked by transition metal dichalcogenides (TMDs) monolayers enable the generation of long-lived interlayer excitons (IXs) with a large binding energy of about 150 meV1 and a long diffusion distance over five micrometers[2], further extending the already appealing properties of the constituent TMDs monolayers
Since IXs are composed of electrons and holes that are resided in neighboring layers, their physical properties strongly depend on the layer configurations and external fields or dopings[3,4]
Summary
Introduction Van derWaals heterostructures (HSs) stacked by transition metal dichalcogenides (TMDs) monolayers enable the generation of long-lived interlayer excitons (IXs) with a large binding energy of about 150 meV1 and a long diffusion distance over five micrometers[2], further extending the already appealing properties of the constituent TMDs monolayers. Since IXs are composed of electrons and holes that are resided in neighboring layers, their physical properties strongly depend on the layer configurations and external fields or dopings[3,4]. Through electrical field or doping, we can modulate the emission intensity and wavelength of the IXs5, and even switch its polarization[6]. IXs in TMDs-based heterostructures carry valley-polarized information and would find promising applications in valleytronics taking advantage of their long lifetime[9]. Previous studies have demonstrated that IXs exhibit a large valley-polarization degree that can be tuned in a wide range by external electric field[10], magnetic field[11], and twist-angle engineering[12]. We demonstrate an IX-based nonvolatile valley-addressable memory, which would prompt relevant investigations on valleytronics
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