Effect of inversion asymmetry on the superconducting and exciton condensates of bilayer graphene

Xiang Hu; Enrico Rossi; Yafis Barlas

doi:10.1103/fw3r-pcw5

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Effect of inversion asymmetry on the superconducting and exciton condensates of bilayer graphene

Xiang Hu, Enrico Rossi, Yafis Barlas

DOI 10.1103/fw3r-pcw5 · Physical Review B

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Abstract

Inversion asymmetry in bilayer graphene can be tuned by the displacement field. As a result, the band dispersion in biased bilayer graphene acquires flatband regions near the Dirac points along with a nontrivial band geometry. We analyze the effect of inversion asymmetry on the critical temperature and superfluid stiffness of the superconducting state of AB-stacked graphene bilayer and the exciton condensate in double layers formed by two AB-stacked graphene bilayers. We find that the geometric superfluid stiffness in bilayer graphene superconductors is negligible due to the small superconducting gap. Furthermore, since the geometric superfluid stiffness is maximized for a constant order parameter, it can be neglected in biased bilayer graphene superconductors with any pairing symmetry. In contrast, the displacement field enhances the geometric superfluid stiffness in exciton condensates. It is most prominent at low densities and high displacement fields. A consequence of the geometric superfluid stiffness is a modest enhancement of the Berezinskii-Kosterlitz-Thouless transition temperature in bilayer graphene's exciton condensate.