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

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.

- changed the last sentence in the abstract - rewrote Sec. II.A - added references 11,18 and 29 - changed styles in Fig.4, Fig.5 and Fig.6 to improve coherence - revised Fig.7 promoted insets to individual panels and added polynomial extrapolation of the self-energy data - Rewrote Sec. III.B. - Rewrote parts of the appendix - added Refs. 19-21