Translation Invariant Bipolaron Theory of Superconductivity and Spectroscopic Experiments

TL;DR

This paper proposes a translation-invariant bipolaron theory to explain the superconducting gap in high-temperature superconductors, clarifying discrepancies among experimental measurements and providing natural explanations for observed spectral features.

Contribution

It introduces a bipolaron-based framework that accounts for different experimental gap measurements and explains spectral phenomena in HTSC.

Findings

Tunneling measures bipolaron energy as the superconducting gap

ARPES measures phonon frequency related to electron-phonon interaction

Explains spectral features like kinks, angular dependence, and pseudogap

Abstract

The explanation of the nature of superconducting gap in high temperature superconductors (HTSC) is a fundamental task which solution can lead to the understanding of superconducting mechanism. However, it has not been fully solved yet. From the mid of the twentieth century when Bardeen, Cooper and Schrieffer constructed their theory it has been believed that a superconducting gap is a collective phenomenon of electron excitations. In this work it is demonstrated that according to translation-invariant bipolaron theory of HTSC the different types of experiments measure for the gap different values. Thus tunneling experiments determine the bipolaron energy for a superconducting gap. On the other hand, the angle - resolved photoemission spectroscopy method measures the phonon frequency for which the electron-phonon interaction is maximum. Such effects as kinks in spectral measurements of gap, its angular dependence, existence of pseudogap and others have got natural explanations.