Dynamics of the normal-superconductor phase transition and the puzzle of the Meissner effect

TL;DR

This paper analyzes the dynamics of the phase transition between normal and superconducting states, highlighting inconsistencies in conventional theory and proposing that hole superconductivity theory better explains the Meissner effect.

Contribution

It demonstrates that conventional BCS-London theory cannot account for observed phenomena during the phase transition and advocates for the hole superconductivity theory as a better explanation.

Findings

Supercurrent flows opposite to the Faraday electric field during phase growth.

A macroscopic torque acts on the body during magnetic field expulsion.

Conventional theory cannot explain the charge motion and torque observed.

Abstract

The analisis of Pippard \cite{pip} for the growth of the normal phase into the superconducting phase in the presence of a magnetic field $H>H_c$ is applied in reverse to the case $H<H_c$ ($H_c=$critical magnetic field). We carry out the analysis both for a planar and a cylindrical geometry. As the superconducting phase grows into the normal phase, a supercurrent is generated at the superconductor-normal phase boundary that flows in direction opposite to the Faraday electric field resulting from the moving phase boundary. This supercurrent motion is in direction opposite to what is dictated by the Lorentz force on the current carriers, and in addition requires that mechanical momentum of opposite sign be tranferred to the system as a whole to ensure momentum conservation. In the cylindrical geometry case, a macroscopic torque of unknown origin acts on the body as a whole as the magnetic field is expelled. We argue that the conventional BCS-London theory of superconductivity cannot explain these facts, and that as a consequence the Meissner effect remains unexplained within the conventional theory of superconductivity. We propose that the Meissner effect can only be understood by assuming that there is motion of charge in direction perpendicular to the normal-superconductor phase boundary and point out that the unconventional theory of hole superconductivity describes this physics