Enhancement of Exciton-Phonon Scattering from Monolayer to Bilayer WS2
Journal article, 2018

Layered transition metal dichalcogenides exhibit the emergence of a direct bandgap at the monolayer limit along with pronounced excitonic effects. In these materials, interaction with phonons is the dominant mechanism that limits the exciton coherence lifetime. Exciton-phonon interaction also facilitates energy and momentum relaxation, and influences exciton diffusion under most experimental conditions. However, the fundamental changes in the exciton-phonon interaction are not well understood as the material undergoes the transition from a direct to an indirect bandgap semiconductor. Here, we address this question through optical spectroscopy and microscopic theory. In the experiment, we study room-temperature statistics of the exciton line width for a large number of mono- A nd bilayer WS2 samples. We observe a systematic increase in the room-temperature line width of the bilayer compared to the monolayer of 50 meV, corresponding to an additional scattering rate of รข0.1 fs-1. We further address both phonon emission and absorption processes by examining the temperature dependence of the width of the exciton resonances. Using a theoretical approach based on many-body formalism, we are able to explain the experimental results and establish a microscopic framework for exciton-phonon interactions that can be applied to naturally occurring and artificially prepared multilayer structures.

scattering lifetime

2D materials


excitonâ'phonon interaction


A. Raja

Stanford University

Kavli Energy NanoSciences Institute

M. Selig

Technische Universität Berlin

Gunnar Berghäuser

Chalmers, Physics, Condensed Matter Theory

Jaeeun Yu

Columbia University in the City of New York

Heather M. Hill

Stanford University

Columbia University in the City of New York

Albert F. Rigosi

Columbia University in the City of New York

Stanford University

Louis E. Brus

Columbia University in the City of New York

A. Knorr

Technische Universität Berlin

T. F. Heinz

Stanford University

Ermin Malic

Chalmers, Physics, Condensed Matter Theory

A. Chernikov

University of Regensburg

Nano Letters

1530-6984 (ISSN) 1530-6992 (eISSN)

Vol. 18 10 6135-6143

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics





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