FisMat2017 - Submission - View

Abstract's title: Large-scale quantum Monte Carlo study of semimetal-superconductor phase transition in Dirac fermions
Submitting author: Yuichi Otsuka
Affiliation: RIKEN Advanced Institute for Computational Science
Affiliation Address: 7-1-26, Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
Country: Japan
Oral presentation/Poster (Author's request): Poster
Other authors and affiliations: Kazuhiro Seki (SISSA), Seiji Yunoki (RIKEN), Sandro Sorella (SISSA)

The Dirac fermions have attracted much interests in condensed matter physics. In addition to their non-trivial phenomena even in non-interacting cases, much attentions have recently been focused on the many-body effects from a theoretical point of view. Especially, it has been recognized that the interacting Dirac fermions offer ideal platforms to study quantum criticality of phase transitions involving the fermionic degree of freedom, which is difficult in systems with the full Fermi surface. In this work, we investigate a semimetal-superconductor phase transition of Dirac fermions by means of large-scale QMC simulations  for the attractive Hubbard model on the triangular lattice, in which alternating magnetic pi-flux is introduced to construct the linear dispersion of the Dirac fermions. This phase transition is expected to correspond to the chiral-XY class in the framework of the Gross-Neveu model, where an order parameter breaking the U(1) symmetry brings about the chiral-symmetry breaking and hence a mass gap. We calculate the order parameter of the s-wave superconductivity on fairly large clusters  and obtain the critical exponents of the transition.