Dynamical signatures and control of time-reversal breaking in twisted nodal superconductors
Abstract
Recent observations of time-reversal breaking superconductivity at twisted cuprate interfaces motivate the development of new approaches to better characterize this emergent phenomenon. Here we study the dynamical properties of the order parameters at the twisted unconventional superconductor interfaces. We reveal the emergence of a soft collective mode (Josephson plasmon) at the time-reversal breaking transition, which can be tuned by temperature, twist angle or magnetic field. Furthermore, nonlinear dynamical responses are shown to contain direct signatures of both the transition and the broken symmetry itself. In particular, we show that second harmonic generation is a necessary and sufficient condition for the symmetry breaking. We discuss the signatures of our predictions in AC current-driven experiments and show that strong nonlinear driving allows to induce dynamical phase transitions between phases with and without spontaneous symmetry breaking.