Observation of tightly bound trions in monolayer MoS2

TL;DR

This paper reports the spectroscopic observation of tightly bound negative trions in doped monolayer MoS2, revealing quasi-particles with large binding energy that are significant at room temperature and have potential for opto-electronic applications.

Contribution

It provides the first spectroscopic identification of negative trions in monolayer MoS2, highlighting their unique properties and potential applications in valleytronics and many-body physics.

Findings

Identification of negative trions with ~20 meV binding energy

Tightly bound trions can be created with valley and spin polarized holes

Trions are significant at room temperature due to their large binding energy

Abstract

Two-dimensional (2D) atomic crystals, such as graphene and transition-metal dichalcogenides, have emerged as a new class of materials with remarkable physical properties. In contrast to graphene, monolayer MoS2 is a non-centrosymmetric material with a direct energy gap. Strong photoluminescence, a current on-off ratio exceeding 10^8 in field-effect transistors, and efficient valley and spin control by optical helicity have recently been demonstrated in this material. Here we report the spectroscopic identification in doped monolayer MoS2 of tightly bound negative trions, a quasi-particle composed of two electrons and a hole. These quasi-particles, which can be created with valley and spin polarized holes, have no analogue in other semiconducting materials. They also possess a large binding energy (~ 20 meV), rendering them significant even at room temperature. Our results open up new avenues both for fundamental studies of many-body interactions and for opto-electronic and valleytronic applications in 2D atomic crystals.