Planckian superconductor

Abstract

The Planckian relaxation rate $\hbar/t_\mathrm{P} = 2\pi k_\mathrm{B} T$ sets a characteristic time scale for both equilibration of quantum critical systems and maximal quantum chaos. In this note, we show that at the critical coupling between a superconducting dot and the complex Sachdev-Ye-Kitaev model, known to be maximally chaotic, the pairing gap $\Delta$ behaves as $\eta \,\, \hbar/t_\mathrm{P}$ at low temperatures, where $\eta$ is an order one constant. The lower critical temperature emerges with a further increase of the coupling strength so that the finite $\Delta$ domain is settled between the two critical temperatures.