Imaging Seebeck drift of excitons and trions in MoSe2 monolayers

Abstract

Hyperspectral imaging at cryogenic temperatures is used to investigate exciton and trion propagation in MoSe${}_2$ monolayers encapsulated with hexagonal boron nitride (hBN). Under a tightly focused, continuous-wave laser excitation, the spatial distribution of neutral excitons and charged trions strongly differ at high excitation densities. Remarkably, in this regime the trion distribution develops a halo shape, similar to that previously observed in WS2 monolayers at room temperature and under pulsed excitation. In contrast, the exciton distribution only presents a moderate broadening without the appereance of a halo. Spatially and spectrally resolved luminescence spectra reveal the buildup of a significant temperature gradient at high excitation power, that is attributed to the energy relaxation of photoinduced hot carriers. We show, via a numerical resolution of the transport equations for excitons and trions, that the halo can be interpreted as thermal drift of trions due to a Seebeck term in the particle current. The model shows that the difference between trion and exciton profiles is simply understood in terms of the very different lifetimes of these two quasiparticles.

References in corpus (5)

• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Tightly bound excitons in monolayer WSe2
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Ultra-low power threshold for laser induced changes in optical properties of 2D Molybdenum dichalcogenides
• Imaging charge and spin diffusion of minority carriers in GaAs

Cited by in corpus (4)

• Exciton optics, dynamics and transport in atomically thin semiconductors
• Electron recoil effect in electrically tunable MoSe2 monolayers
• Two dimensional semiconductors: optical and electronic properties
• Trion-phonon interaction in atomically thin semiconductors