Strong Interaction Effects at a Fermi Surface in a Model for Voltage-Biased Bilayer Graphene

TL;DR

This study uses Monte Carlo simulations to explore the complex interaction effects at the Fermi surface in voltage-biased bilayer graphene, revealing non-canonical scaling and a strongly interacting scenario with a significant superfluid gap.

Contribution

It provides the first calculation of the quasiparticle dispersion relation in this model, demonstrating strong interactions and a superfluid gap comparable to the chemical potential.

Findings

Non-canonical scaling of bulk observables near the quantum critical point

Extraction of Fermi momentum and superfluid gap at different chemical potentials

Support for a strongly interacting scenario with a large superfluid gap

Abstract

Monte Carlo simulation of a 2+1 dimensional model of voltage-biased bilayer graphene, consisting of relativistic fermions with chemical potential mu coupled to charged excitations with opposite sign on each layer, has exposed non-canonical scaling of bulk observables near a quantum critical point found at strong coupling. We present a calculation of the quasiparticle dispersion relation E(k) as a function of exciton source j in the same system, employing partially twisted boundary conditions to boost the number of available momentum modes. The Fermi momentum k_F and superfluid gap Delta are extracted in the limit j tends to zero for three different values of mu, and support a strongly interacting scenario at the Fermi surface with Delta of order O(mu). We propose an explanation for the observation mu < k_F in terms of a dynamical critical exponent z < 1.