Superconductivity from purely repulsive interactions in the strong coupling approach : Application of the SU(2) slave-rotor theory to the Hubbard model

TL;DR

This paper introduces a novel mechanism for superconductivity driven by purely repulsive interactions in the strong coupling regime, utilizing the SU(2) slave-rotor theory to explain pseudogap states and phase fluctuations.

Contribution

It applies the SU(2) slave-rotor approach to the Hubbard model to reveal a new superconducting mechanism with separated energy scales for pairing and coherence.

Findings

Identification of a pseudogap state with local but not global Cooper pair coherence

Superfluid weight decreases linearly with temperature due to phase fluctuations

Separation of energy scales for pairing amplitude and phase coherence

Abstract

We propose a mechanism of superconductivity from purely repulsive interactions in the strong coupling regime, where the BCS (Bardeen-Cooper-Schrieffer) mechanism such as the spin-fluctuation approach is difficult to apply. Based on the SU(2) slave-rotor representation of the Hubbard model, we find that the single energy scale for the amplitude formation of Cooper pairs and their phase coherence is separated into two energy scales, allowing the so called pseudogap state where such Cooper pairs are coherent locally but not globally, interpreted as realization of the density-phase uncertainty principle. This superconducting state shows the temperature-linear decreasing ratio of superfluid weight, resulting from strong phase fluctuations.