Atomically thin mirrors made of monolayer semiconductors

TL;DR

This paper demonstrates that a monolayer of MoSe2 can act as an electrically switchable mirror with high reflectance at cryogenic temperatures, enabling new opportunities in quantum optics and miniaturized optical devices.

Contribution

It shows that monolayer MoSe2 can serve as a highly reflective, electrically tunable mirror due to excitonic coherence, with nonlinear optical properties demonstrated under various excitation conditions.

Findings

Reflects up to 85% of incident light at cryogenic temperatures

Exhibits power- and wavelength-dependent nonlinearities

Enables exploration of quantum nonlinear optics and topological photonics

Abstract

Transition metal dichalcogenide monolayers are promising candidates for exploring new electronic and optical phenomena and for realizing atomically thin optoelectronic devices. They host tightly bound electron-hole pairs (excitons) that can be efficiently excited by resonant light fields. Here, we demonstrate that a single monolayer of molybdenum diselenide (MoSe2) can dramatically modify light transmission near the excitonic resonance, acting as an electrically switchable mirror that reflects up to 85% of incident light at cryogenic temperatures. This high reflectance is a direct consequence of the excellent coherence properties of excitons in this atomically thin semiconductor, encapsulated by hexagonal boron nitride. Furthermore, we show that the MoSe2 monolayer exhibits power- and wavelength-dependent nonlinearities that stem from exciton-based lattice heating in the case of continuous-wave excitation and exciton-exciton interactions when fast, pulsed laser excitation is used. These observations open up new possibilities for studying quantum nonlinear optical phenomena and topological photonics, and for miniaturizing optical devices.