2025/02/18 by Noah J. Jabusch, Emmanouil K. Kokkinis, Jabusch, Noah J. +3 · 1 citation
Physics and Astronomy · Materials Science · #Physics of Superconductivity and Magnetism #Iron-based superconductors research #Theoretical and Computational Physics
paper · pdf · doi:10.1103/physrevb.111.174507
We consider a superconductor under external perturbation, which forces Cooper pairs to develop with a finite total momentum q. The condensation energy of such a state decreases with q and vanishes at a critical qc. We analyze how superconducting order evolves at q\ensuremath≈qc. In three dimensions, the result is well known: the pairing susceptibility diverges at q=qc+0, and the gap amplitude \mathrm\ensuremathΔ(q) gradually increases as q decreases below qc and reaches its largest value \mathrm\ensuremathΔ0 at q=0. In two dimensions (2D), we find different behavior. Namely, for a parabolic dispersion, the pairing susceptibility also diverges at q=qc+0, but at q=qc\ensuremath-0, the gap amplitude jumps to the maximal \mathrm\ensuremathΔ0 and remains equal to it for all q<qc. For a nonparabolic dispersion \ensuremathεk=ck^2\ensuremathα, we find that for \ensuremathα>1 the transition becomes second order, but the gap evolution is rather sharp, whereas for \ensuremathα<1 it becomes first order, but \mathrm\ensuremathΔ(q) is nonmonotonic. This is similar, but not identical, to the behavior of magnetization near a Stoner transition in 2D.