Manipulating topology of quantum phase transitions by symmetry enhancement

Oct 7, 2024
6 pages
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Abstract: (arXiv)
Topology plays a cardinal role in explaining phases and quantum phase transitions beyond the Landau-Ginzburg-Wilson paradigm. In this study, we formulate a set of models of Dirac fermions in 2+1 dimensions with SU(NN)×\timesSU(2)×\timesU(1) symmetry that have the potential to host critical points described by field theories with topological terms. For N=2N=2 it shows a rich phase diagram containing semimetallic, quantum spin Hall insulating, Kekulé valence bond solid and s-wave superconducting phases and features multiple Landau-Ginzburg-Wilson phase transitions driven by interaction strength. At N=1N=1 a deconfined quantum critical point is observed. At N=2N=2 one expects the critical theory to correspond to a level 2 Wess-Zumino-Witten theory in 2+1 dimensions. Here the numerical results however show a strong first order transition. Another transition can be governed by a topological θ\theta-term which is rendered irrelevant for even values of NN thus leading to Landau-Ginzburg-Wilson behaviour.
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  • 6 pages main text + 7 pages Supplemental Material, 3 figures main text + 9 figures Supplemental Material