Constraining Forces Stabilizing Superconductivity in Bismuth

TL;DR

This paper discusses a nonadiabatic quantum mechanical mechanism involving constraining forces that stabilize Cooper pairs in superconductors, including bismuth, challenging traditional attractive interaction models.

Contribution

It provides evidence that constraining forces in the nonadiabatic Heisenberg model are responsible for superconductivity in bismuth, supporting their broader role in all superconductors.

Findings

Superconducting state in bismuth linked to narrow, half-filled band.

Constraining forces stabilize Cooper pairs in bismuth.

Supports nonadiabatic mechanism as key to superconductivity.

Abstract

As shown in former papers, the nonadiabatic Heisenberg model presents a novel mechanism of Cooper pair formation generated by the strongly correlated atomic-like motion of the electrons in narrow, roughly half-filled "superconducting bands". These are energy bands represented by optimally localized spin-dependent Wannier functions adapted to the symmetry of the material under consideration. The formation of Cooper pairs is not the result of an attractive electron-electron interaction but can be described in terms of quantum mechanical constraining forces constraining the electrons to form Cooper pairs. There is theoretical and experimental evidence that only this nonadiabatic mechanism operating in superconducting bands may produce eigenstates in which the electrons form Cooper pairs. These constraining forces stabilize the Cooper pairs in any superconductor, whether conventional or unconventional. Here we report evidence that also the experimentally found superconducting state in bismuth at ambient as well as at high pressure is connected with a narrow, roughly half-filled superconducting band in the respective band structure. This observation corroborates once more the significance of constraining forces in the theory of superconductivity.