Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Superconductivity: Theory
TT 38.4: Vortrag
Freitag, 9. September 2022, 10:15–10:30, H23
Degenerate plaquette physics as key ingredient of high-temperature superconductivity in cuprates — Mikhail Danilov1, van Loon Erik G. C. P.2, •Brener Sergey1,3, Iskakov Sergey4, Katsnelson Mikhail5, and Lichtenstein Alexander1,3 — 1Institute of Theoretical Physics, University of Hamburg — 2Department of Physics, Lund University — 3The Hamburg Centre for Ultrafast Imaging — 4Department of Physics, University of Michigan — 5Radboud University, Institute for Molecules and Materials
A major pathway towards understanding complex systems is given by exactly solvable reference systems that contain the essential physics of the system. For the t−t′−U Hubbard model, the four-site plaquette is known to have a point in the U−µ space where states with electron occupations N=2, 3, 4 per plaquette are degenerate. Such a degenerate point causes strong fluctuations when a lattice of plaquettes is constructed. The next-nearest-neighbour hopping is shown to play a crucial role in the formation of strongly bound electronic bipolarons whose coherence at lower temperature could be the explanation for superconductivity. A complementary approach to the lattice of plaquettes is given by dual fermion perturbation theory starting from a single degenerate plaquette as a reference system. This perturbation theory already contains the relevant short-ranged fluctuations from the beginning via the two-particle correlations of the plaquette. We find that d-wave superconductivity remains a leading instability channel under a reasonably broad range of parameters.