Long Tailed Trions in Monolayer MoS2: Exploring Many-body Physics through Temperature Dependent Photoluminescence

Speaker: Jason Christopher

When: April 28, 2016 (Thu), 12:30PM to 01:30PM (add to my calendar)
Location: PRB 365

This event is part of the Preliminary Oral Exam.

Examining Committee: Bennett Goldberg, Anna Swan, Claudio Chamon, Ami Katz

Abstract: Monolayer molybdenum disulfide (MoS2) has emerged as an ideal material for exploring many-body physics, because of its two in-equivalent, direct gap valleys and exotic bound states. Here we focus on one such bound state, the trion, which consists of two electrons and a hole. Unlike excitons, trions can radiatively decay with non-zero momentum by kicking out an electron. This simple difference from excitons results in an asymmetric trion photoluminescence (PL) peak with a long low energy tail. The tail length depends on two factors: one for the trion momentum distribution and another for the structure of the bound state. We use temperature to alter the momentum distribution and thus separate these two factors. Our detailed analysis reveals the trion effective radius and binding energy, as well as the ratio of the effective hole mass to electron mass. By including the trion's long tail in our analysis we are also able to separate the exciton and trion contributions to the PL spectra more accurately providing greater insight into the temperature dependence of the band gap and spin-orbit splitting of the valence band. The analysis and concepts presented here are applicable to other atomically thin transition metal dichalcogenides (TMDC) where trions have been observed such as molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2).