Dissipationless electron transport, multicomponent superfluidity, and the superfluid BCS-BEC crossover in electron-hole double bilayer graphene
Prof.dr. David Neilson (University of Camerino, Italy, and University of New South Wales, Sidney, Australia)
The recent observation in zero magnetic field of electron-hole superfluidity at temperatures of a few Kelvin in a pair of atomically close (1-2 nanometre separation) yet electrically isolated, n- and p-doped bilayer graphene sheets, as had been proposed in Ref. , raises exciting prospects in the quest for heat-free electron transport in nano devices and for the investigation of the superfluid BCS-BEC crossover in a solid state device. By sweeping the carrier densities using metallic gates, the long-range Coulomb pairing interaction strength can be continuously tuned through the crossover regime. The perpendicular electric field from the gates opens up small and continuously tuneable band gaps between the conduction and valence bands of each sheet. Interesting physics effects arise from the long-range nature of the superfluid pairing interaction, from the associated competition between screening and superfluidity (the condensate pairs are neutral)[4, 5], from multicondensate effects arising from the small band gaps, and from the potential for high transition temperatures, exploiting the extremely strong pairing interactions. I will attempt to provide an overview of each of these issues.
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 L´opez R´ıos, P., Andrea, P., Needs, R. J. & Neilson, D. ,Phys. Rev. Lett. (2018). (to appear).
 Conti, S., Perali, A., Peeters, F. M. & Neilson, D. , Phys. Rev. Lett. 119, 257002 (2017).