SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 63: Superconductivity: Theory

TT 63.3: Vortrag

Freitag, 31. März 2023, 10:00–10:15, HSZ 103

Correction to Morel-Anderson-Tolmachev pseudopotential from nonlocal Coulomb interaction in 2D superconductors — •Manuel Simonato, Mikhail I. Katsnelson, and Malte Rösner — Radboud University, Nijmegen, NL

The repulsive Coulomb interaction between electrons is detrimental to conventional superconductivity. The widely accepted model to account for this is to describe this repulsion with a purely local interaction of strength µ_C. Morel, Anderson, and Tolmachev then showed that the superconducting quantities are effectively described by a renormalized parameter µ_C^*, as a direct consequence of the energy scale separation between phonons and electrons. In 2D the screening properties are less efficient and modeling the Coulomb repulsion with a strictly local interaction can result in inaccurate description. We therefore study how superconducting properties are affected by nonlocal Coulomb repulsions. We find that the superconducting state can still be accurately described when a revised Coulomb pseudopotential µ_C^* is used. We show that the revised parameter, which accounts for nonlocal interactions, is always larger that the convetional µ_C^*. The non-local Coulomb interaction thus suppresses superconductivity and the critical temperature even further. Analyzing the Bethe-Salpeter equation describing the screening of Coulomb interaction in 2D, we obtain an analytical expression for µ_C^*, and show that the structure of the nonlocal Coulomb interaction weakens the screening effects from high-energy pair fluctuations and therefore yields larger values of the pseudopotential.