Competitive density waves in quasi-one-dimensional electron systems

TL;DR

This paper explores how electron-electron and electron-phonon interactions in a one-dimensional t-J model lead to various lattice and charge modulated ground states, revealing a complex phase diagram with competing insulating phases.

Contribution

It provides a detailed analysis of the ground states of the t-J model with phonons, including phase diagrams and the effects of different coupling strengths, using both analytical and numerical methods.

Findings

Identification of competing spin-Peierls and dimerized states.

Phase diagram showing paramagnetic band insulator and Mott insulator regions.

Analytical and numerical characterization of ground states.

Abstract

We investigate the nature of the ground state of the one-dimensional t-J model coupled to adiabatic phonons by use of the Lanczos technique at quarter filling. Due to the interplay between electron-electron and electron-phonon interactions, the model undergoes instabilities toward the formation of lattice and charge modulations. Moderate on-site and intra-site electron-phonon couplings lead to a competition of different spin-Peierls and dimerized states. In the former case two electrons belong to the unit cell and we expect a paramagnetic band insulator state, while lattice dimerization leads to a Mott insulating state with quasi long range antiferromagnetic order. The zero temperature phase diagram is obtained as a function of intra-site and inter-site electron-phonon couplings, analytically in the $J\to 0$ limit and numerically at finite J/t.