Strain Control of Exciton-Phonon Coupling in Atomically Thin Semiconductors
Journal article, 2018

Semiconducting transition metal dichalcogenide (TMDC) monolayers have exceptional physical properties. They show bright photoluminescence due to their unique band structure and absorb more than 10% of the light at their excitonic resonances despite their atomic thickness. At room temperature, the width of the exciton transitions is governed by the exciton-phonon interaction leading to strongly asymmetric line shapes. TMDC monolayers are also extremely flexible, sustaining mechanical strain of about 10% without breaking. The excitonic properties strongly depend on strain. For example, exciton energies of TMDC monolayers significantly redshift under uniaxial tensile strain. Here, we demonstrate that the width and the asymmetric line shape of excitonic resonances in TMDC monolayers can be controlled with applied strain. We measure photoluminescence and absorption spectra of the A exciton in monolayer MoSe 2 , WSe 2 , WS 2 , and MoS 2 under uniaxial tensile strain. We find that the A exciton substantially narrows and becomes more symmetric for the selenium-based monolayer materials, while no change is observed for atomically thin WS 2 . For MoS 2 monolayers, the line width increases. These effects are due to a modified exciton-phonon coupling at increasing strain levels because of changes in the electronic band structure of the respective monolayer materials. This interpretation based on steady-state experiments is corroborated by time-resolved photoluminescence measurements. Our results demonstrate that moderate strain values on the order of only 1% are already sufficient to globally tune the exciton-phonon interaction in TMDC monolayers and hold the promise for controlling the coupling on the nanoscale.

Transition metal dichalcogenide

excitons

strain

exciton-phonon coupling

line width

Author

Iris Niehues

University of Münster

R. Schmidt

University of Münster

Matthias Drüppel

University of Münster

Philipp Marauhn

University of Münster

Dominik Christiansen

Technische Universität Berlin

M. Selig

Technische Universität Berlin

Gunnar Berghäuser

Chalmers, Physics, Condensed Matter Theory

Daniel Wigger

University of Münster

R. Schneider

University of Münster

Lisa Braasch

University of Münster

Rouven Koch

University of Münster

Andres Castellanos-Gomez

CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)

Tilmann Kuhn

University of Münster

A. Knorr

Technische Universität Berlin

Ermin Malic

Chalmers, Physics, Condensed Matter Theory

Michael Rohlfing

University of Münster

S. M. de Vasconcellos

University of Münster

R. Bratschitsch

University of Münster

Nano Letters

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

Vol. 18 3 1751-1757

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics

DOI

10.1021/acs.nanolett.7b04868

More information

Latest update

4/3/2018 1