･The origin of the phase variable for superconductivity is the Berry connection arising from many-body wave functions
･In the new theory, the role of electron-pairing is to stabilize the nontrivial Berry connection
Abstract
Although the standard theory of superconductivity based on the BCS theory is a successful one, several experimental results indicate the necessity for a fundamental revision. We argue that the revision is on the origin of the phase variable for superconductivity; this phase appears as a consequence of the electron-pairing in the standard theory, but its origin is a Berry connection arising from many-body wave functions. When this Berry connection is non-trivial, it gives rise to a collective mode that generates supercurrent; this collective mode creates number-changing operators for particles participating in this mode, and these number-changing operators stabilize the superconducting state by exploiting the Cooper instability. In the new theory, the role of the electron-pairing is to stabilize the nontrivial Berry connection; it is not the cause of superconductivity. In BCS superconductors, however, the simultaneous appearance of the nontrivial Berry connection and the electron-pairing occurs. Therefore, the electron-pairing amplitude can be used as an order parameter for the superconducting state. We revisit the Andreev$-$Saint-James reflection and the Josephson effect. They are explained as consequence of the presence of the Berry connection. Bogoliubov quasiparticles are replaced by the particle-number conserving Bogoliubov excitations that describe the transfer of electrons between the collective mod and single particle mode.
Benefit
Based on the calculation of the “Berry connection,” this model helps explain new experimental results to elucidate Cuprate Superconductivity better than the BCS theory.
Market Application
Superconducting devices, Quantum bit, Next-generation memory,
Publications
https://arxiv.org/abs/2103.00805
IP
Date: Jun 17th, 2011
Number: US9224099
Status: Granted
URL: https://worldwide.espacenet.com/publicationDetails/originalDocument?FT=D&date=20151229&DB=&locale=jp_EP&CC=US&NR=9224099B2&KC=B2&ND=4
Other
https://www.tsukuba.ac.jp/en/research-news/20210709140000.html
https://koizumi-h.github.io
