Central Charge of Periodically Driven Critical Kitaev Chains*

Periodically driven Kitaev chains show a rich phase diagram as the amplitude and frequency of the drive is varied, with topological phase transitions separating regions with different number of Majorana zero and π modes. We explore whether the critical point separating different phases of the periodically driven chain may be characterized by a universal central charge. We affirmatively answer this question by studying the entanglement entropy (EE) numerically, and analytically for the lowest entangled many particle eigenstate at arbitrary non-stroboscopic and stroboscopic times. We find that the EE at the critical point scales logarithmically with a time-independent central charge, and that the Floquet micro-motion gives only sub-leading corrections to the EE. This result also generalizes to multi-critical points where the EE is found to have a central charge which is the sum of the central charges of the intersecting critical lines.