Abnormal heavy-flux flow in cuprate superconductors

TL;DR

This paper introduces a new method to analyze nonlocal charge fluxes in cuprate superconductors, revealing their role in high-temperature superconductivity and reproducing experimental flat band features.

Contribution

A novel computational approach to identify anharmonically coupled phonons as generators of nonlocal flux flows in cuprates, linking flux strength to superconducting transition temperature.

Findings

Nonlocal fluxes correlate with T_(c,max) in cuprates

Heavy fluxes tunnel through a dynamic energy band near the Fermi level

Reproduces flat band features below Tc in simulations

Abstract

Dynamic charge transfers, or charge fluxes, generated by anharmonic phonon couplings have previously shown some fundamental connections with the pseudogap phase and other important phases in cuprate superconductors. The anharmonicity here suggests the importance of nonadiabatic behaviors of charge fluxes in cuprates. These charge fluxes will result in the dynamic charge transfer that can be directly calculated by the charge difference induced by phonons in density functional theory simulations. However, retrieving the flux field from the calculated charge transfer is nontrivial. In this article, a new method is developed to solve these fluxes, which help identify anharmonically coupled phonons as the generator of nonlocal flux flows beyond local oscillations in cuprates, especially at high frequencies. A strength metric of such nonlocal fluxes shows a strong correlation to the maximum superconducting transition temperature T_(c,max) of different cuprate families. A unique picture is thus proposed where heavy fluxes tunnel through a dynamic energy band near the Fermi level, providing the attraction force through a Bernoulli-like mechanism for the formation of Cooper pairs. Adding the dynamic band to our band simulation also reproduces the flat band feature that appears below the superconducting transition temperature Tc in previous experimental measurements.