Zusammenfassung
Propagation of light-emitting quasiparticles is of centralimportanceacross the fields of condensed matter physics and nanomaterials science.We experimentally demonstrate diffusion of excitons in the presenceof a continuously tunable Fermi sea of free charge carriers in a monolayersemiconductor. Light emission from tightly bound exciton states inelectrically gated WSe2 monolayer is detected using ...
Zusammenfassung
Propagation of light-emitting quasiparticles is of centralimportanceacross the fields of condensed matter physics and nanomaterials science.We experimentally demonstrate diffusion of excitons in the presenceof a continuously tunable Fermi sea of free charge carriers in a monolayersemiconductor. Light emission from tightly bound exciton states inelectrically gated WSe2 monolayer is detected using spatiallyand temporally resolved microscopy. The measurements reveal a nonmonotonicdependence of the exciton diffusion coefficient on the charge carrierdensity in both electron and hole doped regimes. Supported by analyticaltheory describing exciton-carrier interactions in a dissipativesystem, we identify distinct regimes of elastic scattering and quasiparticleformation determining exciton diffusion. The crossover region exhibitsa highly unusual behavior of an increasing diffusion coefficient withincreasing carrier densities. Temperature-dependent diffusion measurementsfurther reveal characteristic signatures of freely propagating excitoniccomplexes dressed by free charges with effective mobilities up to3 x 10(3) cm(2)/(V s).
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