TY - JOUR

T1 - Spin and valley dynamics of excitons in transition metal dichalcogenide monolayers

AU - Glazov, M. M.

AU - Ivchenko, E. L.

AU - Wang, G.

AU - Amand, T.

AU - Marie, X.

AU - Urbaszek, B.

AU - Liu, B. L.

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Monolayers of transition metal dichalcogenides, namely, molybdenum and tungsten disulfides and diselenides demonstrate unusual optical properties related to the spin-valley locking effect. Particularly, excitation of monolayers by circularly polarized light selectively creates electron-hole pairs or excitons in non-equivalent valleys in momentum space, depending on the light helicity. This allows studying the inter-valley dynamics of charge carriers and Coulomb complexes by means of optical spectroscopy. Here, we present a concise review of the neutral exciton fine structure and its spin and valley dynamics in monolayers of transition metal dichalcogenides. It is demonstrated that the long-range exchange interaction between an electron and a hole in the exciton is an efficient mechanism for rapid mixing between bright excitons made of electron-hole pairs in different valleys. We discuss the physical origin of the long-range exchange interaction and outline its derivation in both the electrodynamical and k·p approaches. We further present a model of bright exciton spin dynamics driven by an interplay between the long-range exchange interaction and scattering. Finally, we discuss the application of the model to describe recent experimental data obtained by time-resolved photoluminescence and Kerr rotation techniques. Kerr rotation dynamics at T=4K for a σ+ and σ- pump beam in WSe2. Inset: Schematics of the optical selection rules of the excitons photogenerated from charge carriers in K± valleys and their coupling induced by the long-range exchange interaction.

AB - Monolayers of transition metal dichalcogenides, namely, molybdenum and tungsten disulfides and diselenides demonstrate unusual optical properties related to the spin-valley locking effect. Particularly, excitation of monolayers by circularly polarized light selectively creates electron-hole pairs or excitons in non-equivalent valleys in momentum space, depending on the light helicity. This allows studying the inter-valley dynamics of charge carriers and Coulomb complexes by means of optical spectroscopy. Here, we present a concise review of the neutral exciton fine structure and its spin and valley dynamics in monolayers of transition metal dichalcogenides. It is demonstrated that the long-range exchange interaction between an electron and a hole in the exciton is an efficient mechanism for rapid mixing between bright excitons made of electron-hole pairs in different valleys. We discuss the physical origin of the long-range exchange interaction and outline its derivation in both the electrodynamical and k·p approaches. We further present a model of bright exciton spin dynamics driven by an interplay between the long-range exchange interaction and scattering. Finally, we discuss the application of the model to describe recent experimental data obtained by time-resolved photoluminescence and Kerr rotation techniques. Kerr rotation dynamics at T=4K for a σ+ and σ- pump beam in WSe2. Inset: Schematics of the optical selection rules of the excitons photogenerated from charge carriers in K± valleys and their coupling induced by the long-range exchange interaction.

KW - Exchange interaction

KW - Excitons

KW - Optical orientation

KW - Spin dynamics

KW - Transition metal dichalcogenides

KW - Valleytronics

UR - http://www.scopus.com/inward/record.url?scp=84946429453&partnerID=8YFLogxK

U2 - 10.1002/pssb.201552211

DO - 10.1002/pssb.201552211

M3 - Article

AN - SCOPUS:84946429453

VL - 252

SP - 2349

EP - 2362

JO - Physica Status Solidi (B): Basic Research

JF - Physica Status Solidi (B): Basic Research

SN - 0370-1972

IS - 11

ER -