Maximal quantum chaos of the critical Fermi surface

We investigate the many-body quantum chaos of non-Fermi liquid states in two spatial dimensions by computing their out-of-time-order correlation functions. Using a recently proposed large-N theory for the critical Fermi surface, and the ladder identity of Gu and Kitaev, we show that the chaos Lyapunov exponent takes the maximal value of 2 π T, where T is the absolute temperature.