Possible charge instabilities in two-dimensional doped Mott insulators

TL;DR

This paper investigates charge instabilities in doped two-dimensional Mott insulators, revealing dominant d-wave charge density wave and nematic phases, with tendencies towards inhomogeneity and phase separation, using a large-N expansion of the t-J model.

Contribution

It introduces a large-N path integral approach to analyze charge instabilities in the 2D t-J model, highlighting the prominence of flux and nematic phases under various conditions.

Findings

d-wave charge density wave as leading instability

electronic nematic phase as next leading instability

phase separation near half-filling

Abstract

Motivated by the growing evidence of the importance of charge fluctuations in the pseudogap phase in high-temperature cuprate superconductors, we apply a large-N expansion formulated in a path integral representation of the two-dimensional t-J model on a square lattice. We study all possible charge instabilities of the paramagnetic state in leading order of the 1/N expansion. While the d-wave charge density wave (flux phase) becomes the leading instability for various choices of model parameters, we find that a d-wave Pomeranchuk (electronic nematic phase) instability occurs as a next leading one. In particular, the nematic state has a strong tendency to become inhomogeneous. In the presence of a large second nearest-neighbor hopping integral, the flux phase is suppressed and the electronic nematic instability becomes leading in a high doping region. Besides these two major instabilities, bond-order phases occur as weaker instabilities close to half-filling. Phase separation is also detected in a finite temperature region near half-filling.