Dirac Fermions with Competing Mass Terms: Non-Landau Transition with Emergent Symmetry

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Fakher Assaad
Universit├Ąt W├╝rzburg
Thursday, August 17, 2017 - 2:00pm
402 Old LeConte Hall

There has recently been a flurry of negative sign free fermionic models that exhibit exotic phases and phase transitions. After reviewing these advances, I will place the emphasis on a model of Dirac fermions in 2+1 dimensions with dynamically generated, anti-commuting SO(3) N\'eel and Z2 Kekul\'e mass terms. The phase diagram is obtained from finite-size scaling and includes a direct and continuous transition between N\'eel and Kekul\'e phases. The fermions remain gapped across the transition, and our data support an emergent SO(4) symmetry unifying the two order parameters. This is only one of many negative sign free models with dynamically generated competing mass terms that allow to investigate phase transitions beyond the Ginzburg-Landau-Wilson paradigm.