Exciton diffusion in monolayer semiconductors with suppressed disorder
Journal article, 2020

Tightly bound excitons in monolayer semiconductors represent a versatile platform to study two-dimensional propagation of neutral quasiparticles. Their intrinsic properties, however, can be severely obscured by spatial energy fluctuations due to a high sensitivity to the immediate environment. Here, we take advantage of the encapsulation of individual layers in hexagonal boron nitride to strongly suppress environmental disorder. Diffusion of excitons is then directly monitored using time and spatially resolved emission microscopy at ambient conditions. We consistently find very efficient propagation with linear diffusion coefficients up to 10 cm(2)/s, corresponding to room-temperature effective mobilities as high as 400 cm(2)/Vs as well as a correlation between rapid diffusion and short population lifetime. At elevated densities we detect distinct signatures of many-particle interactions and consequences of strongly suppressed Auger-type exciton-exciton annihilation. A combination of analytical and numerical theoretical approaches is employed to provide pathways toward comprehensive understanding of the observed linear and nonlinear propagation phenomena. We emphasize the role of dark exciton states and present a mechanism for diffusion facilitated by free-electron hole plasma from entropy-ionized excitons.

Author

Jonas Zipfel

University of Regensburg

Marvin Kulig

University of Regensburg

Raul Perea Causin

Condensed Matter and Materials Theory

Samuel Brem

Condensed Matter and Materials Theory

Jonas D. Ziegler

University of Regensburg

Roberto Rosati

Condensed Matter and Materials Theory

Takashi Taniguchi

National Institute for Materials Science (NIMS)

Kenji Watanabe

National Institute for Materials Science (NIMS)

Mikhail M. Glazov

Ioffe Phys Tech Inst

Ermin Malic

Condensed Matter and Materials Theory

Alexey Chernikov

University of Regensburg

PHYSICAL REVIEW B

2469-9950 (ISSN) 2469-9969 (eISSN)

Vol. 101 11 115430

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics

DOI

10.1103/PhysRevB.101.115430

More information

Latest update

5/20/2020