Valley engineering electron-hole liquids in TMDC monolayers

TL;DR

This paper explores how valley physics in MoS2 monolayers can be used to control electron-hole liquid properties, potentially enabling tunable optoelectronic devices at room temperature.

Contribution

It introduces a model showing the feasibility of phase transition into EHLs in substrate-supported MoS2 monolayers, highlighting a new route for tunability.

Findings

EHLs can form in supported monolayer MoS2 under certain conditions.

Valley physics enables tuning of EHL characteristics such as emission wavelength.

Room temperature EHL formation is possible with high crystal purity and proper substrate support.

Abstract

Electron-hole liquids(EHLs), a correlated state of matter and a thermodynamic liquid, have recently been found to exist at room temperature in suspended monolayers of MoS2. Appreciably higher rates of radiative recombination inside the liquid as compared to free excitons hold promise for optoelectronic applications such as broadband lasing. In this paper, we show that leveraging the valley physics in MoS2 may be a route towards achieving tunability of specific characteristics of an EHL, such as emission wavelength, linewidth, and most importantly, the liquid density. The conditions under which EHLs form, in bulk semiconductors as well as TMDC monolayers are quite stringent, requiring high crystal purity and cryogenic temperatures in bulk semiconductors, and suspension in monolayers. Using a simple yet powerful model for describing free excitons and show that a phase transition into the EHL state may be feasible in substrate-supported monolayer samples. More repeatable experimental realizations of EHLs may be essential to answer questions regarding the nature of electron-hole correlations and how they may be used to generate non-trivial states of light.