Valley-selective exciton bistability in a suspended monolayer semiconductor

TL;DR

This paper reports on the observation of robust, power- and wavelength-dependent optical bistability in suspended monolayer WSe2, driven by photo-thermal effects, with polarization-controlled switching enabled by magnetic fields.

Contribution

It introduces a novel demonstration of exciton bistability in monolayer WSe2 with helicity-dependent control under magnetic fields, highlighting a new mechanism for optical switching.

Findings

Optical bistability observed at 10^3 W/cm^2 in suspended WSe2.

Bistability driven by photo-thermal nonlinearity and feedback.

Helicity-dependent switching enabled by magnetic field.

Abstract

We demonstrate robust power- and wavelength-dependent optical bistability in fully suspended monolayers of WSe2 near the exciton resonance. Bistability has been achieved under continuous-wave optical excitation at an intensity level of 10^3 W/cm^2. The observed bistability is originated from a photo-thermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. Under a finite magnetic field, the exciton bistability becomes helicity dependent, which enables repeatable switching of light purely by its polarization.