Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Superconductivity: Theory

TT 34.5: Vortrag

Mittwoch, 19. März 2025, 16:00–16:15, H36

Obstructed pairs with zero superfluid stiffness — •Tamaghna Hazra and Jörg Schmalian — Karslruhe Institute of Technology

We present a microscopic pairing mechanism in which the kinetic energy of pairs is much lower than the kinetic energy of electrons. This results in interaction-driven localization of charge without extrinsic disorder and is characterized by a vanishing superfluid stiffness. Localized pairs gain more kinetic energy from resonating between sublattices in a bosonic compact localized state, than from delocalizing throughout the material. This is grounded in a microscopic model building on a structural motif shared by many oxide superconductors - strongly interacting localized electrons realize spin degrees of freedom on the vertices and doped charge lives on the edges of the Bravais lattice. In the strong-coupling limit, local unconventional pairs realize the bosonic analogue of flat bands supported on line graphs. We discuss the experimental implications of this pairing mechanism, with concrete falsifiability criteria, and emphasize the broad scope of this recipe in connection to diverse families of strongly correlated materials which share the key ingredients that go into it.

Keywords: Superfluid stiffness; Flat band superconductivity; Localization without extrinsic disorder; Superconducting puddles; Bosonic flat bands