Superconducting fluctuations and charge-4$e$ plaquette state at strong coupling

TL;DR

This paper investigates phase correlations in a microscopic model with spin-singlet pairing, revealing a charge-4$e$ plaquette state at strong coupling that competes with superconductivity and affects spectroscopic properties.

Contribution

It introduces a phase mutual information approach to map the phase diagram and uncovers a novel charge-4$e$ plaquette state at strong coupling.

Findings

Identification of a charge-4$e$ plaquette state at strong coupling.

Development of a phase diagram including multiple regions.

Agreement with experimental spectroscopic observations.

Abstract

We apply the static auxiliary field Monte Carlo approach to study phase correlations of the pairing fields in a microscopic model with spin-singlet pairing interaction. We find that the short- and long-range phase correlations are well captured by the phase mutual information, which allows us to construct a theoretical phase diagram containing the uniform $d$-wave superconducting region, the phase fluctuating region, the local pairing region, and the disordered region. We show that the gradual development of phase coherence has a number of consequences on spectroscopic measurements, such as the development of the Fermi arc and the anisotropy in the angle-resolved spectra, scattering rate, entropy, specific heat, and quasiparticle dispersion, in good agreement with experimental observations. For strong coupling, our Monte Carlo simulation reveals an unexpected charge-4$e$ plaquette state with $d$-wave bonds, which competes with the uniform $d$-wave superconductivity and exhibits a U-shaped density of states.