Informal DQMP seminar

Carte non disponible

Day / Time
Date(s) - 19/03/2015
13 h 30 min - 14 h 30 min

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Auditoire Stückelberg, Ecole de physique

19 March 2015 (Thursday), 13h30

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Prof. Michael Fogler
Department of Physics, University of California, San Diego

Indirect excitons in atomically thin heterostructures

In the wake of graphene, a number of other ultrathin crystals have become a subject of active research. Such (quasi) 2D crystals are typically made of atomic layers weakly coupled together by van der Waals (vdW) interaction. These novel solids range widely in electronic properties, from insulators to semiconductors to metals. An ambitious goal is to use 2D vdW crystals as building blocks of artificially stacked heterostructures in which new functionalities can arise. In this talk I will discuss theoretical calculations and some preliminary experimental evidence of indirect excitons in a specially designed vdW structure. The main elements of the structure are two monolayers of a transition metal dichalcogenides separated by an atomically thin spacer of boron nitride. Larger effective mass of indirect excitons in vdW heterostructures and a smaller dielectric constant of these materials compared to those of conventional semiconductors, such as GaAs,  lead to indirect exciton binding energies of ~120 meV, according to the calculations. It is therefore expected that indirect exciton in these novel structures can survive at temperatures well above the room temperature. Particularly tantalizing is the prospect to realize experimentally a degenerate Bose gas of indirect excitons that would exhibit a macroscopic occupation of a quantum state and vanishing viscosity at temperatures as high as 100 K. I will discuss our incipient progress and the remaining obstacles on the path toward this goal.

 

[1] M.M. Fogler, L.V. Butov & K.S. Novoselov, “High-temperature superfluidity with indirect excitons in van der Waals heterostructures”, Nature Communications, 5, 4555 (1914).

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