Charge susceptibility in the t-J model

TL;DR

This paper investigates the momentum and doping dependence of charge susceptibility in the t-J model, revealing how correlations, pairing, and long-range interactions influence charge fluctuations and electron-phonon coupling in cuprates.

Contribution

It provides new insights into the momentum-dependent renormalization of charge susceptibility and the effects of pairing and t' hopping in the t-J model, with implications for cuprate physics.

Findings

Charge susceptibility near ( , b1) is suppressed at low doping.

Charge susceptibility around ( , 0) remains large across doping levels.

Charge inhomogeneity may be promoted by pseudogap formation.

Abstract

Momentum and doping dependence of the static charge susceptibility \chi(q) in the t-t'-J model is investigated. Correlations lead to a strongly momentum dependent renormalization of \chi(q). The charge susceptibility near (\pi,\pi) region of the Brillouin zone is strongly suppressed as the hole density \delta is decreased. However, contrary to naive expectations, \chi(q) around q = (\pi,0) and (0,\pi) remains large and practically unchanged at \delta \sim 0.1-0.5. This effect is consistent with a tendency towards low-energy charge fluctuations with the wave vectors along the \Gamma-X direction, reported in earlier studies. Our main finding is that the above trends are amplified by J-driven pairing effects, indicating that the pseudogap formation may promote the charge inhomogeneity. The next-nearest hopping t' leads to weakening of the above momentum-selective renormalizations of \chi(q). We analyze the effects of long-range Coulomb interaction, taking into account a layered structure of cuprates. As an application, the results are discussed in the context of bond-stretching phonon softening in hole-doped cuprates. In particular, a peculiar doping and momentum dependence of the electron-phonon coupling constant is found.