Quantum Geometric Superconductivity: Non-equilibrium and Finite Temperature
ORAL · Invited
Abstract
We have found that superconductivity and superfluidity are connected to quantum geometry [1]: the superfluid weight in a multiband system is proportional to the minimal quantum metric of the band. The quantum metric is connected to the Berry curvature, which relates superconductivity to the topological properties of the band. Using this theory, we have shown that superconductivity is possible also in a flat band where individual electrons would not move. These results may be essential in explaining the observation of superconductivity in twisted bilayer graphene [2]. The temperature dependence of the superfluid weight shows a power-law behavior according to our dynamical mean-field theory calculations [3]. The quantum transport in flat band shows unique behavior [4]: while supercurrent can flow, quasiparticle transport is highly suppressed even in non-equilibrium conditions. This may have important consequences for superconducting devices. We have predicted that flat band systems as part of Josephson junctions can lead to behavior distinct from the dispersive case [5]. We have also found that quantum geometry governs Bose-Einstein condensates in flat bands [6].
[1] S. Peotta, P. Törmä, Nature Commun. 6, 8944 (2015); K.-E. Huhtinen, J. Herzog-Arbeitman, A. Chew, B.A. Bernevig, P. Törmä, Phys. Rev. B 106, 014518 (2022).
[2] A. Julku, T.J. Peltonen, L. Liang, T.T. Heikkilä, P. Törmä, Phys. Rev. B 101, 060505(R) (2020); X. Hu, T. Hyart, D.I. Pikulin, E. Rossi, Phys. Rev. Lett. 123, 237002 (2019); F. Xie, Z. Song, B. Lian, B.A. Bernevig, Phys. Rev. Lett. 124, 167002 (2020); P. Törmä, S. Peotta, B.A. Bernevig, Nat. Rev. Phys. 4, 528 (2022).
[3] R.P.S. Penttilä, K.-E. Huhtinen, P. Törmä, arXiv:2404.12993 (2024).
[4] V.A.J. Pyykkönen, S. Peotta, P. Törmä, Phys. Rev. Lett. 130, 216003 (2023).
[5] P. Virtanen, R.P.S. Penttilä, P. Törmä, A. Díez-Carlón, D.K. Efetov, T.T. Heikkilä, arXiv:2410.23121 (2024).
[6] A. Julku, G.M. Bruun, P. Törmä, Phys. Rev. Lett., 127, 170404 (2021).
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Publication: [1] S. Peotta, P. Törmä, Nature Commun. 6, 8944 (2015); K.-E. Huhtinen, J. Herzog-Arbeitman, A. Chew, B.A. Bernevig, P. Törmä, Phys. Rev. B 106, 014518 (2022).<br>[2] A. Julku, T.J. Peltonen, L. Liang, T.T. Heikkilä, P. Törmä, Phys. Rev. B 101, 060505(R) (2020); X. Hu, T. Hyart, D.I. Pikulin, E. Rossi, Phys. Rev. Lett. 123, 237002 (2019); F. Xie, Z. Song, B. Lian, B.A. Bernevig, Phys. Rev. Lett. 124, 167002 (2020); P. Törmä, S. Peotta, B.A. Bernevig, Nat. Rev. Phys. 4, 528 (2022).<br>[3] R.P.S. Penttilä, K.-E. Huhtinen, P. Törmä, arXiv:2404.12993 (2024).<br>[4] V.A.J. Pyykkönen, S. Peotta, P. Törmä, Phys. Rev. Lett. 130, 216003 (2023).<br>[5] P. Virtanen, R.P.S. Penttilä, P. Törmä, A. Díez-Carlón, D.K. Efetov, T.T. Heikkilä, arXiv:2410.23121 (2024).<br>[6] A. Julku, G.M. Bruun, P. Törmä, Phys. Rev. Lett., 127, 170404 (2021).
Presenters
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Paivi Torma
Aalto University
Authors
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Paivi Torma
Aalto University