Charge fluctuations close to phase separation in the two dimensional t-J model

TL;DR

This study uses Green Function Monte Carlo simulations to analyze the two-dimensional t-J model, finding no phase separation in the relevant doping range for high-temperature superconductors, but observing enhanced fluctuations near an instability.

Contribution

It provides the first accurate energy calculations in large lattices and links fluctuation behavior to experimental observations near phase separation.

Findings

No phase separation in the physical region for HTc superconductors.

Enhanced fluctuations at incommensurate wavevectors near the phase separation instability.

Scaling of fluctuations with doping matches experimental data.

Abstract

We have studied the t-J model using the Green Function Monte Carlo technique. We have obtained accurate energies well converged in the thermodynamic limit, by performing simulations up to 242 lattice sites. By studying the energy as a function of hole doping we conclude that there is no phase separation in the physical region, relevant for HTc superconductors. This finding is further supported by the hole-hole correlation function calculation. Remarkably, by approaching the phase separation instability, for $J_c/t\sim 0.5$,this function displays enhanced fluctuations at incommensurate wavevectors, scaling linearly with the doping, in agreement with experimental findings.