Emergence of Charge Loop Current in Geometrically Frustrated Hubbard Model: Functional Renormalization Group Study

TL;DR

This study uncovers a spin-fluctuation-driven charge loop current mechanism in a frustrated Hubbard model, revealing that cLC can emerge near magnetic criticality and may have higher transition temperatures than d-wave superconductivity.

Contribution

It introduces a novel cLC mechanism driven by spin fluctuations in a frustrated Hubbard model, analyzed via functional renormalization group theory.

Findings

cLC appears between AFM and dSC phases.

cLC transition temperature can exceed dSC temperature.

Strong forward scatterings g2 and g4 drive cLC formation.

Abstract

Spontaneous current orders due to odd-parity order parameters attract increasing attention in various strongly correlated metals. Here, we discover a novel spin-fluctuation-driven charge loop current (cLC) mechanism based on the functional renormalization group (fRG) theory. The present mechanism leads to the ferro-cLC order in a simple frustrated chain Hubbard model. The cLC appears between the antiferromagnetic and $d$-wave superconducting ($d$SC) phases. While the microscopic origin of the cLC has a close similarity to that of the $d$SC, the cLC transition temperature $T_{\rm cLC}$ can be higher than the $d$SC one for wide parameter range. Furthermore, we reveal that the ferro cLC order is driven by the strong enhancement of the forward scatterings $g_2$ and $g_4$ owing to the two dimensionality based on the $g$-ology language. The present study indicates that the cLC can emerge in metals near the magnetic criticality with geometrical frustration