TY - JOUR

T1 - Exciton diffusion in monolayer semiconductors with suppressed disorder

AU - Zipfel, Jonas

AU - Kulig, Marvin

AU - Perea-Causin, Raul

AU - Brem, Samuel

AU - Ziegler, Jonas D.

AU - Rosati, Roberto

AU - Taniguchi, Takashi

AU - Watanabe, Kenji

AU - Glazov, Mikhail M.

AU - Malic, Ermin

AU - Chernikov, Alexey

PY - 2020/3/15

Y1 - 2020/3/15

N2 - 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.

AB - 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.

KW - TRANSITION

KW - PHOTOLUMINESCENCE

KW - IONIZATION

KW - TRANSPORT

KW - DYNAMICS

UR - http://www.scopus.com/inward/record.url?scp=85083217180&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/5fa8d506-5252-3665-b4c7-8abc4d2e6312/

U2 - 10.1103/PhysRevB.101.115430

DO - 10.1103/PhysRevB.101.115430

M3 - статья

VL - 101

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 11

M1 - 115430

ER -