Quantum Monte Carlo simulation of two-dimensional Emery model

TL;DR

This paper uses Quantum Monte Carlo simulations to study the two-dimensional Emery model of CuO2 planes, revealing electronic transitions, metal-insulator transitions, and magnetic structures relevant to high-temperature superconductors.

Contribution

It applies a direct-space Quantum Monte Carlo method to the Emery model, providing new insights into electronic, magnetic, and conductive properties at various dopings.

Findings

Specific heat peaks indicate electronic transitions.

Metal-insulator transitions observed in conductivity curves.

Fermions form antiferromagnetic loops or chains depending on doping.

Abstract

The Quantum Monte Carlo simulation of the two-dimensional Emery model of the CuO2 plane of hight Tc superconductors were performed. The method based on the direct-space proposed by Suzuki and Hirsch was used. Contrary to the method based on the Hubbard-Stratonovich transformation, the states generated by this method are basis states in occupation number representation, i. e. configurations of fermions can be observed on real two-dimensional array.Energy and specific heat were computed for different dopings. Specific heat curves show peaks at low temperature which could be assigned to electronic transitions. Quantity similar to current-current correlation function were computed. The static electric conductivity curves obtained by this way show metal-insulator transitions and two different metallic behaviours. On the direct-space states generated at low temperature and zero doping, the fermions form antiferromagnetic loops while they form antiferromagnetic chains for other dopings. The loops seem to appear when the conductivity becomes zero while yhe conductivity increases with the numbers of chains but superconductivity is not unambiguously evident.