A Dynamical Quantum Cluster Approach to Two-Particle Correlation Functions in the Hubbard Model

TL;DR

This paper extends the Dynamical Cluster Approximation to compute two-particle response functions in the 2D Hubbard model, revealing insights into charge and spin excitations in strongly correlated regimes.

Contribution

It introduces an effective vertex approximation within DCA for two-particle functions, enabling analysis of charge and spin dynamics in the Hubbard model.

Findings

Consistent description of charge and spin excitations near optimal doping.

Agreement with high-temperature quantum Monte Carlo data.

Insights into the interplay between charge, spin, and single-particle excitations.

Abstract

We investigate the charge- and spin dynamical structure factors for the 2D one-band Hubbard model in the strong coupling regime within an extension of the Dynamical Cluster Approximation (DCA) to two-particle response functions. The full irreducible two-particle vertex with three momenta and frequencies is approximated by an effective vertex dependent on the momentum and frequency of the spin/charge excitation. In the spirit of the DCA, the effective vertex is calculated with quantum Monte Carlo methods on a finite cluster. On the basis of a comparison with high temperature auxiliary field quantum Monte Carlo data we show that near and beyond optimal doping, our results provide a consistent overall picture of the interplay between charge, spin and single-particle excitations.