Temporal Evolution of Low-Temperature Phonon Sidebands in Transition Metal Dichalcogenides

• DOI: 10.1021/acsphotonics.0c00866
• Publication Date: 2020-09-04T14:39:18Z
• Authors: Roberto Rosati; Koloman Wagner; Samuel Brem; Raül Perea-Causín; Edith Wietek; Jonas Zipfel; Jonas D. Ziegler; Malte Selig; Takashi Taniguchi; Kenji Watanabe; Andreas Knorr; Alexey Chernikov; Ermin Malic
• Keywords: Tungsten diselenide; Thermalisation; Picosecond

Low-temperature photoluminescence (PL) of hBN-encapsulated monolayer tungsten diselenide (WSe$_2$) shows a multitude sharp emission peaks below the bright exciton. Some them have been recently identified as phonon sidebands momentum-dark states. However, exciton dynamics behind emergence these has not revealed yet. In this joint theory-experiment study, we theoretically predict and experimentally observe time-resolved PL providing microscopic insights into thermalization hot excitons formed after optical excitation. good agreement between theory experiment, demonstrate spectral red-shift on timescale tens picoseconds reflecting phonon-driven in Furthermore, transient sideband that vanishes stationary PL. The obtained are applicable to broad class 2D materials with multiple valleys.