Topology-Bounded Superfluid Weight in Twisted Bilayer Graphene
ORAL
Abstract
We derive the superfluid weight (phase stiffness) of the TBLG superconducting flat bands with a uniform pairing, and show that it can be expressed as an integral of the Fubini-Study metric of the flat bands. This mirrors results [1] already obtained for nonzero Chern number bands even though the TBLG flat bands have zero Chern number. We further show the metric integral is lower bounded by the topological C2zT Wilson loop winding number of the TBLG flat bands, which renders the superfluid weight has a topological lower bound proportional to the pairing gap. In contrast, trivial flat bands have a zero superfluid weight. The superfluid weight is crucial in determining the BKT transition temperature of the superconductor. Based on the transition temperature measured in TBLG experiments, we estimate the topological contribution of the superfluid weight in TBLG.
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Presenters
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Fang Xie
Princeton University
Authors
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Fang Xie
Princeton University
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Zhida Song
Chinese Academy of Sciences,Institute of Physics, Princeton University, Department of Physics, Princeton University, Physics, Princeton University, Department of Physics, Princeton university, Physics department, Princeton University
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Biao Lian
Princeton Center for Theoretical Science, Princeton University, Princeton University, Physics, Princeton University
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Andrei Bernevig
Physics, Princeton University, Princeton Center for Theoretical Science, Princeton University, Princeton University, Department of Physics, Princeton university, Physics department, Princeton University