Work

Superconductivity with repulsion: A variational approach

Year: 2025

Type: article

Abstract: In the presence of repulsive interactions, the BCS state appears unstable, showing up as a saddle point of the mean-field free energy. This apparent paradox has sparked recent proposals to restore stability by projecting out repulsive modes, effectively restricting the problem to the attractive sector. The authors show here that a Bogoliubov variational construction yields a bounded free energy and stabilizes the BCS state, without constraining the energy landscape. Simple models highlight the role of the full BCS kernel in correctly identifying collective modes, offering a robust framework for multichannel superconductors.

Source: Physical review. B./Physical review. B

DOI: 10.1103/jhy9-mckg

Authors: Laura Fanfarillo, Yifu Cao, Chandan Setty, Sergio Caprara, P. J. Hirschfeld

Institutions: Institute for Complex Systems, University of Florida, Iowa State University, Ames National Laboratory, Sapienza University of Rome

Language: English

Topic: Physics of Superconductivity and Magnetism

Subfield: Condensed Matter Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, Sapienza Università di Roma

Awards: G1871477277, G2018964769, G4904603537, G5807938509, Kavli Institute for Theoretical Physics