Hidden Charge Order of Interacting Dirac Fermions on the Honeycomb Lattice

TL;DR

This paper investigates the extended Hubbard model on a honeycomb lattice, revealing a novel hidden metallic charge order with semi-Dirac excitations, challenging previous assumptions about the nature of the phase transition.

Contribution

It introduces a new type of hidden metallic charge order in the Hubbard model, showing that the transition is not of the expected universality class.

Findings

Collective fluctuations suppress topological states.

Ground state exhibits a hidden metallic charge order.

Transition likely not in the Gross-Neveu universality class.

Abstract

We consider the extended half-filled Hubbard model on the honeycomb lattice for second nearest neighbors interactions. Using a functional integral approach, we find that collective fluctuations suppress topological states and instead favor charge ordering, in agreement with previous numerical studies. However, we show that the critical point is not of the putative semimetal-Mott insulator variety. Due to the frustrated nature of the interactions, the ground state is described by a novel hidden {\it metallic} charge order with {\it semi-Dirac} excitations. We conjecture that this transition is not in the Gross-Neveu universality class.