Generating quantum multicriticality in topological insulators by periodic driving

We demonstrate that the prototypical two-dimensional Chern insulator hosts exotic quantum multicriticality in the presence of an appropriate periodic driving: a linear Dirac-like transition coexists with a quadratic nodal looplike transition. This nodal loop gap closure is characterized by an enhanced chiral-mirror symmetry that is induced by the driving procedure. The existence of multiple universality classes can be unambiguously captured by extracting critical exponents and scaling laws with a single renormalization group approach based on the curvature function of the stroboscopic Floquet Hamiltonian. This procedure is effective regardless of whether the topological phase transitions are associated with anomalous edge modes or not. We comment on possible experimental realizations of the model and detection schemes for the curvature function.