SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 48: Topological Superconductors
TT 48.1: Vortrag
Donnerstag, 30. März 2023, 09:30–09:45, HSZ 304
Superconductivity mediated by topological phonons — •Alessio Zaccone — Department of Physics, University of Milan, 20133 Milano, Italy
Topological phononic insulators are the counterpart of three-dimensional quantum spin Hall insulators in phononic systems and, as such, their phononic topological surfaces are characterized by Dirac cone-shaped gapless edge states arising as a consequence of a bulk-boundary correspondence. We proposed [1] a theoretical framework for the possible superconductivity in these materials, where the attractive interaction between electrons is mediated by topological phonons in nontrivial boundary modes. Within the BCS limit, we developed a self-consistent two-band gap equation, whose solutions show that the superconducting Tc has a nonmonotonic behavior with respect to the phononic frequency in the Kramers-like point. This remarkable behavior is produced by a resonance that occurs when electrons and phonons on the topological surfaces have the same energy: this effectively increases the electron-phonon interaction and hence the Cooper pair binding energy, thus establishing an optimal condition for the superconducting phase. With this mechanism, the Tc can be increased by well over a factor 2, and the maximum enhancement occurs in the degenerate phononic flat-band limit.
[1] D. Di Miceli, C. Setty, A. Zaccone, Phys. Rev. B 106, 054502 (2022)