Phonon-driven nodal surface superconductivity of Fermi arcs

Giorno 4 giugno 2026, con inizio alle ore 11:00, presso l'Aula T del DFA, su invito del Prof. F. M. D. Pellegrino, il Prof. Francesco Buccheri (Leibniz Institute for Solid State and Materials Research, Dresden, Germany) terrà un seminario dal titolo Phonon-driven nodal surface superconductivity of Fermi arcs.

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Abstract. According to recent observations the topological surface states of Weyl semimetals, their Fermi arcs, may develop a superconducting gap, while bulk superconductivity remains absent. What drives the formation of this novel superconducting state is an open question. I will argue that surface superconductivity in time-reversal-invariant Weyl semimetals can arise from the interaction of Fermi arc electrons with both surface and bulk phonons. Employing a low-energy Hamiltonian including Coulomb repulsion and electron-phonon interactions, I will present an effective theory on the Fermi arcs. The combined effect of the Fermi arcs being disconnected and weak screening of the Coulomb repulsion at the system's surface causes nodes to appear in the superconducting gap, in accordance with recent photoelectron spectroscopy experiments on PtBi2. This suggests that engineering the Coulomb screening, e.g. by a surface layer coating, may strongly affect the critical temperature, as well as size and even symmetry of the surface superconducting gap.