Why holes are not like electrons. III. How holes in the normal state turn into electrons in the superconducting state

TL;DR

This paper clarifies how hole carriers in the normal state transform into electron-like carriers in the superconducting state, linking electron-electron and electron-ion interactions to the phenomenon of charge expulsion in superconductors.

Contribution

It demonstrates that the same interactions responsible for pairing and undressing of holes also cause their transformation into electrons and charge expulsion, supporting the hole superconductivity theory.

Findings

Holes behave like electrons in the superconducting state due to interaction effects

Carrier undressing involves both electron-electron and electron-ion interactions

Superconductors expel negative charge as part of the transition

Abstract

In recent work, we discussed the difference between electrons and holes in energy band in solids from a many-particle point of view, originating in the electron-electron interaction[1], and from a single particle point of view, originating in the electron-ion interaction[2]. We proposed that superconductivity in solids only occurs when the Fermi level is close to the top of a band (hole carriers), that it originates in `undressing' of carriers from $both$ the electron-electron and the electron-ion interaction, and that as a consequence holes in the normal state behave like electrons in the superconducting state[3]. However, the connection between both undressing effects was left unclear, as was left unclear how the transformation from hole behavior to electron behavior occurs. Here we clarify these questions by showing that the same electron-electron interaction physics that promotes pairing of hole carriers and undressing of carriers from the electron-electron interaction leads to undressing of carriers from the electron-ion interaction and transforms the behavior of carriers from hole-like to electron-like. Furthermore this phenomenon is connected with the expulsion of negative charge that we predict to occur in superconductors. These unexpected connections support the validity of our theoretical framework, the theory of hole superconductivity, to explain superconductivity in solids.