Multicomponent electron-hole superfluidity and the BCS-BEC crossover in double bilayer graphene

Abstract

Superfluidity in coupled electron-hole sheets of bilayer graphene is predicted here to be multicomponent because of the conduction and valence bands. We investigate the superfluid crossover properties as functions of the tunable carrier densities and the tunable energy band gap $E_g$. For small band gaps there is a significant boost in the two superfluid gaps, but the interaction driven excitations from the valence to the conduction band can weaken the superfluidity, even blocking the system from entering the BEC regime at low densities. At a given larger density, a band gap $E_g\sim 40$-$60$ meV can carry the system into the strong-pairing multiband BCS-BEC crossover regime, the optimal range for realization of high-$T_c$ superfluidity.

5 pages, 4 figures

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• A doping-dependent switch from one- to two-component superfluidity at temperature above 100K in coupled electron-hole Van der Waals heterostructures
• Tunneling and Fluctuating Electron-Hole Cooper Pairs in Double Bilayer Graphene
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• Biexciton-like quartet condensates in an electron-hole liquid
• Multiband Mechanism for the Sign Reversal of Coulomb Drag Observed in Double Bilayer Graphene Heterostructures
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• Excitonic insulators and superfluidity in 2D bilayers without external fields
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• Exciton Superfluidity in 2D Heterostructures from First Principles: The importance of material specific screening
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• Anderson-Bogoliubov and Carlson-Goldman modes in counterflow superconductors: Case study of a double monolayer graphene
• Topological fluctuating electron-hole Cooper pairs in graphene-GaAs heterostructures
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