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

Date: 20 September 2017

Venue: UAntwerpen, Campus Groenenborger, Room U.247 - Groenenborgerlaan 171 - 2020 Antwerpen (route: UAntwerpen, Campus Groenenborger)

Time: 4:00 PM - 5:00 PM

Organization / co-organization: Condensed Matter Theory

Short description: Condensed Matter Theory seminar presented by Sara Conti



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

Abstract

Coupled electron-hole sheets of bilayer graphene have been proposed as a system to observe high-temperature superfluidity.  This system has recently been fabricated. We study the effects on the pairing of the multibands of bilayer graphene and of the  energy band gap that can be tuned by external electric fields. We investigate the superfluid BEC-BCS crossover properties as  functions of the electron and hole densities and the tunable energy band gap.

For small band gaps, we find that interaction  driven excitations from the valence band to the conduction band can block the system from entering the BEC regime even at  very low densities. For large band gaps Van Hove singularities magnify the ratio Δ/EF and suppress excitations from the valence  band. Both these effects push the system toward the strongly coupled BEC regime, the optimal range for high-TC superfluidity.



Contact email: lucian.covaci@uantwerpen.be

Link: http://cmt.uantwerpen.be