Work

Enhanced superconductivity in proximity to peaks in densities of states

Year: 2026

Type: article

Abstract: For the BCS theory of superconductivity, the electron-phonon interaction is transformed to an attractive electron-electron interaction in the vicinity of the Fermi energy only. At the same time, its formal derivation using a unitary transformation reveals that the electrons attract one another whenever their energies do not differ by more than the phonon energy ω D , independent of closeness to the Fermi energy. Consequently, the order parameter becomes finite even away from the Fermi level. Yet, for small interactions, its magnitude is usually small and can be safely ignored, justifying the BCS approximation. Intriguingly, we find that an accumulation of density of states at an energy ɛ peak in proximity to the Fermi energy induces a significant order parameter magnitude around ɛ peak , which exceeds the one at E F for moderate coupling strengths. This strong enhancement is heralded by the softening of an additional collective mode, which resembles a second phase transition. We predict measurable signatures in the thermodynamic and spectroscopic responses to this unexpected phenomenon, guiding future experimental searches for it. Finally, we demonstrate that these signatures remain robust upon including a phenomenological Coulomb repulsion, indicating that the enhancement is not an artifact of the idealized model.

Source: Physical Review Research

DOI: 10.1103/xbsf-8l6q

Authors: Joshua Althüser, Ilya M. Eremin, Götz S. Uhrig

Institutions: TU Dortmund University, Ruhr University Bochum

Language: English

Topic: Physics of Superconductivity and Magnetism

Subfield: Condensed Matter Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,625

Funder: Mercator Research Center Ruhr