Topological phase transitions with SO(4) symmetry in (2+1)d interacting Dirac fermions

TL;DR

This study uses quantum Monte Carlo simulations to explore interaction-driven topological phase transitions in (2+1)d Dirac semimetals, revealing complex phase behavior including second-order, first-order, and nodal line formations with SO(4) symmetry enhancement.

Contribution

It introduces a model coupling Dirac fermions to Ising spins and maps out the phase diagram, highlighting novel topological transitions and symmetry enhancements not previously characterized.

Findings

Identified second-order Ising quantum phase transition at weak coupling.

Observed first-order topological phase transition with Dirac points smearing into nodal lines.

Found strong SO(4) symmetry fluctuations at certain phase boundaries.

Abstract

Interaction-driven topological phase transitions in Dirac semimetals are investigated by means of large-scale quantum Monte Carlo (QMC) simulations. The interaction among Dirac fermions is introduced by coupling them to Ising spins that realize the quantum dynamics of the two-dimensional transverse field Ising model. The ground state phase diagram, in which the tuning parameters are the transverse field and the coupling between fermion and Ising spins, is determined. At weak and intermediate coupling, a second-order Ising quantum phase transition and a first-order topological phase transition between two topologically distinct Dirac semimetals are observed. Interestingly, at the latter, the Dirac points smear out to form nodal lines in the Brillouin zone, and collective bosonic fluctuations with SO(4) symmetry are strongly enhanced. At strong coupling, these two phase boundaries merge into a first-order transition.