Multiband Dual Fermion Approach to Quantum Criticality in the Hubbard Honeycomb Lattice

TL;DR

This paper develops a multiband Dual Fermion approach to study quantum criticality in the Hubbard model on the honeycomb lattice, capturing critical fluctuations and estimating phase transition parameters.

Contribution

It introduces a multiband formulation of the Dual Fermion method to analyze quantum critical behavior in the honeycomb lattice Hubbard model, including fluctuation effects beyond local correlations.

Findings

Estimated critical interaction strength for phase transition.

Identified crossover temperature to classical regime.

Demonstrated non-Fermi liquid behavior at large interactions.

Abstract

We study the Hubbard model on the honeycomb lattice in the vicinity of the quantum critical point by means of a multiband formulation of the Dual Fermion approach. Beyond the strong local correlations of the dynamical mean field, critical fluctuations on all length scales are included by means of a ladder diagram summation. Analysis of the susceptibility yields an estimate of the critical interaction strength of the quantum phase transition from a paramagnetic semimetal to an antiferromagnetic insulator, in good agreement to other numerical methods. We further estimate the crossover temperature to the renormalized classical regime. Our data imply that, at large interaction strengths, the Hubbard model on the honeycomb lattice behaves like a quantum nonlinear sigma model, while being in a non-Fermi liquid state.