Quantum Geometry and superconductivity

12.01.2026 13:00 – 14:00

We have found that superconductivity and superfluidity are connected to quantum geometry [1,2]: 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 relevant for explaining the observation of superconductivity in twisted bilayer graphene [3], and rhombohedral graphite [4]. The quantum transport in flat band shows unique behavior [5]: 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 [6]. Our recent results show that superfluid weight in a flat band is robust to disorder, which can be explained by intra- and interband localization functionals [7]. Finally, we report on experimental realization of new superconductors predicted by machine learning [8].


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[2] P Törmä, Phys. Rev. Lett. 131, 240001 (2023); J. Yu, B.A. Bernevig, R. Queiroz, E. Rossi, P. Törmä, B.-J. Yang, njp Quantum Materials 10, 101 (2025).
[3] 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).
[4] G Jiang, T Heikkilä, P Törmä, arXiv:2504.03617 (2025).
[5] V.A.J. Pyykkönen, S. Peotta, P. Törmä, Phys. Rev. Lett. 130, 216003 (2023).
[6] P. Virtanen, R.P.S. Penttilä, P. Törmä, A. Díez-Carlón, D.K. Efetov, T.T. Heikkilä, Phys. Rev. B 112, L100502 (2025); A. Diez-Carlon, J. Diez-Merida, P. Rout, D. Sedov, P. Virtanen, S. Banerjee, R.P.S. Penttilä, P. Altpeter, K. Watanabe, T. Taniguchi, S.-Y. Yang, K.T. Law, T.T. Heikkilä, P. Törmä, M.S. Scheurer, D.K. Efetov, Phys. Rev. X 15, 041033 (2025).
[7] K. Kolář, T.T. Heikkilä, P. Törmä, arXiv:2510.05224 (2025).
[8] R.A. Mustaf, Sajilesh K.P., S. Mishra, J. Deng, Y. Jiang, K.H. Hiorth, E.O. Lamponen, M. Gutierrez-Amigo, P. Törmä, M.A.L. Marques, B.A. Bernevig, E. Morosan, arXiv:2512.16945 (2025).

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Bâtiment: Ecole de Physique

Auditoire Stückelberg

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