Central Charge of Periodically Driven Critical Kitaev Chains

TL;DR

This paper investigates the critical behavior of periodically driven Kitaev chains, demonstrating that their entanglement entropy scales logarithmically with a universal, time-independent central charge at phase transition points.

Contribution

It establishes that the critical points in driven Kitaev chains are characterized by a universal central charge, extending conformal field theory concepts to non-equilibrium Floquet systems.

Findings

Entanglement entropy scales logarithmically at criticality.

Central charge is time-independent and universal.

Multicritical points have additive central charges.

Abstract

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 {\pi} 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 nonstroboscopic and stroboscopic times. We find that the EE at the critical point scales logarithmically with a time-independent central charge, and that the Floquet micromotion gives only subleading corrections to the EE. This result also generalizes to multicritical points where the EE is found to have a central charge that is the sum of the central charges of the intersecting critical lines.