Coupling to optical phonons in the one-dimensional t-J model: Effects on superconducting fluctuations and phase separation

TL;DR

This study investigates how coupling to optical phonons affects superconducting fluctuations and phase separation in the 1D t-J model, revealing that phonons significantly alter the phase diagram and weaken superconducting correlations.

Contribution

It introduces a variational approach to include phonon effects in the 1D t-J model, showing how phonons shift phase boundaries and influence superconducting properties.

Findings

Phonons shift the phase separation boundary to smaller J/t values.

Superconducting fluctuations are weakened by phonon-mediated charge density waves.

The results have implications for understanding high-temperature superconductors.

Abstract

The one-dimensional (1D) $t$-$J$ Holstein model is studied by exact diagonalization of finite rings using a variational approximation for the phonon states. Due to renormalization effects induced by the phonons, for intermediate electron-phonon coupling, the phase separation (PS) boundary, and with it the region of dominating superconducting fluctuations is shifted substantially to smaller values of $J/t$ as compared to the pure $t$-$J$ model. Superconducting correlations are weakened through charge density wave interactions mediated by the phonons. Possible consequences for the high $T_c$ oxides are discussed.