TY - JOUR
T1 - Fragile Topology and Flat-Band Superconductivity in the Strong-Coupling Regime
AU - Peri, Valerio
AU - Song, Zhi Da
AU - Bernevig, B. Andrei
AU - Huber, Sebastian D.
N1 - Funding Information:
This work was supported by a grant from the Swiss National Supercomputing Centre (CSCS) under Project ID No. eth5b. The auxiliary-field QMC simulations were carried out with the alf package. V. P., and S. D. H. acknowledge support from the Swiss National Science Foundation, the NCCR QSIT, and the European Research Council under the Grant Agreement No. 771503 (TopMechMat). Z. S. and B. A. B. are supported by the U.S. Department of Energy Grant No. DE-SC0016239, the Schmidt Fund for Innovative Research, Simons Investigator Grant No. 404513, the Packard Foundation, the National Science Foundation EAGER Grant No. DMR-1643312, NSF-MRSEC Grant No. DMR-1420541, BSF Israel US foundation Grant No. 2018226, ONR Grant No. N00014-20-1-2303, and the Princeton Global Network Funds.
Publisher Copyright:
© 2021 American Physical Society.
PY - 2021/1/14
Y1 - 2021/1/14
N2 - In flat bands, superconductivity can lead to surprising transport effects. The superfluid "mobility", in the form of the superfluid weight Ds, does not draw from the curvature of the band but has a purely band-geometric origin. In a mean-field description, a nonzero Chern number orfragile topology sets a lower bound for Ds, which, via the Berezinskii-Kosterlitz-Thouless mechanism, might explain the relatively high superconducting transition temperature measured in magic-angletwisted bilayer graphene (MATBG). For fragile topology, relevant for the bilayer system, the fate of this bound for finite temperature and beyond the mean-field approximation remained, however, unclear. Here, we numerically use exact Monte Carlo simulations to study an attractive Hubbard model inflat bands with topological properties akin to those of MATBG. We find a superconducting phase transition with a critical temperature that scales linearly with the interaction strength. Then, we investigate the robustness of the superconducting state to the addition of trivial bands that may or may not trivialize the fragile topology. Our results substantiate the validity of the topological bound beyond the mean-field regime and further stress the importance of fragile topology for flat-band superconductivity.
AB - In flat bands, superconductivity can lead to surprising transport effects. The superfluid "mobility", in the form of the superfluid weight Ds, does not draw from the curvature of the band but has a purely band-geometric origin. In a mean-field description, a nonzero Chern number orfragile topology sets a lower bound for Ds, which, via the Berezinskii-Kosterlitz-Thouless mechanism, might explain the relatively high superconducting transition temperature measured in magic-angletwisted bilayer graphene (MATBG). For fragile topology, relevant for the bilayer system, the fate of this bound for finite temperature and beyond the mean-field approximation remained, however, unclear. Here, we numerically use exact Monte Carlo simulations to study an attractive Hubbard model inflat bands with topological properties akin to those of MATBG. We find a superconducting phase transition with a critical temperature that scales linearly with the interaction strength. Then, we investigate the robustness of the superconducting state to the addition of trivial bands that may or may not trivialize the fragile topology. Our results substantiate the validity of the topological bound beyond the mean-field regime and further stress the importance of fragile topology for flat-band superconductivity.
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U2 - 10.1103/PhysRevLett.126.027002
DO - 10.1103/PhysRevLett.126.027002
M3 - Article
C2 - 33512222
AN - SCOPUS:85099878647
SN - 0031-9007
VL - 126
JO - Physical Review Letters
JF - Physical Review Letters
IS - 2
M1 - 027002
ER -