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Volume 256 - 34th annual International Symposium on Lattice Field Theory (LATTICE2016) - Applications Beyond QCD
Competing order in the fermionic Hubbard model on the hexagonal graphene lattice
P. Buividovich, D. Smith, M. Ulybyshev, L. von Smekal*
*corresponding author
Full text: pdf
Pre-published on: 2017 February 23
Published on: 2017 March 24
Abstract
We study the phase diagram of the fermionic Hubbard model on the hexagonal lattice in the space of on-site and nearest neighbor couplings with Hybrid-Monte-Carlo simulations. With pure on-site repulsion this allows to determine the critical coupling strength for spin-density wave formation with the standard approach of introducing a small mass term, explicitly breaking the sublattice symmetry. The analogous mass term for charge-density wave formation above a critical nearest-neighbor repulsion, on the other hand, would introduce a fermion sign problem. The competition between the two and the phase diagram in the space of the two coouplings can however be studied in simulations without explicit sublattice symmetry breaking. Our results compare qualitatively well with the Hartree-Fock phase diagram. We furthermore demonstrate how spin-symmetry breaking by the Euclidean time discretization can be avoided also, when using an improved fermion action based on an exponetial transfer matrix with exact sublattice symmetry.
DOI: https://doi.org/10.22323/1.256.0244
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