Using quantum Monte Carlo simulations we have mapped out the zero-temperature phase diagram of a symmetric electron-hole bilayer with twofold valley degeneracy, as a function of the interlayer distance d and in-layer density n. We find that the effect of the valley degeneracy is to shrink the region of stability of the excitonic condensate, in favor of quadriexcitons at small d and of the four-component plasma at large d, with minor effects on the value of the excitonic condensate fraction. The enclosure of the condensate in a density window possibly explains why anomalous tunneling conductivity, interpreted as a signature of condensation, is observed only between two finite values of carrier density in graphene bilayers. Our phase diagram may provide directions to select device parameters for future experiments.

Quadriexcitons and excitonic condensate in a symmetric electron-hole bilayer with valley degeneracy

De Palo, Stefania
Membro del Collaboration Group
;
Tramonto, F.
Membro del Collaboration Group
;
Moroni, Saverio
Membro del Collaboration Group
;
Senatore, Gaetano
Membro del Collaboration Group
2023-01-01

Abstract

Using quantum Monte Carlo simulations we have mapped out the zero-temperature phase diagram of a symmetric electron-hole bilayer with twofold valley degeneracy, as a function of the interlayer distance d and in-layer density n. We find that the effect of the valley degeneracy is to shrink the region of stability of the excitonic condensate, in favor of quadriexcitons at small d and of the four-component plasma at large d, with minor effects on the value of the excitonic condensate fraction. The enclosure of the condensate in a density window possibly explains why anomalous tunneling conductivity, interpreted as a signature of condensation, is observed only between two finite values of carrier density in graphene bilayers. Our phase diagram may provide directions to select device parameters for future experiments.
2023
26-gen-2023
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https://journals.aps.org/prb/abstract/10.1103/PhysRevB.107.L041409
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3038705
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