Charge fluctuation induced superconducting state in two-dimensional quarter-filled electron systems

TL;DR

This study explores how charge fluctuations influence superconductivity in a two-dimensional quarter-filled extended Hubbard model, revealing a dominant d_{xy} symmetry pairing and reentrant transitions near the superconducting phase.

Contribution

It demonstrates that charge fluctuations can induce a d_{xy} symmetry superconducting state, with a detailed analysis of the pairing interaction and phase transitions.

Findings

Superconducting state with d_{xy} symmetry is dominant across most parameters.

Charge fluctuations can change the pairing interaction from repulsive to attractive.

Reentrant transition occurs near the onset of superconductivity.

Abstract

We investigate the superconducting (SC) state in two-dimensional extended Hubbard model at a quarter-filling with the on-site repulsive interaction ($U$) and the nearest-neighbor one ($V$), which lead to the spin fluctuation and the charge fluctuation, respectively. The effect of the charge fluctuation on the onset of the SC state is calculated by estimating the pairing interaction within the random phase approximation. Solving the linearized Eliashberg equation with the anomalous self-energy as the function of both momentum and frequency, we examined the singlet SC state on the plane of $U$ and $V$ with the fixed temperature. We found a novel result that the SC state with the $d_{xy}$ symmetry retains for most parameters of $U$ and $V$, although the pairing interaction changes the sign from repulsive one into attractive one with increasing $V$. The reentrant transition as the function of temperature occurs close to the onset of the SC state.