From integrability to many-body quantum chaos through a Markovian bath

Abstract: Recent examples have confirmed the common belief that quantum chaos is always suppressed in the presence of an environment. Here we show that this is not always the case. We compute the Lyapunov exponent of a $q$-body Majorana Sachdev-Ye-Kitaev (SYK) model coupled to a Markovian bath. Provided that the jump operators describing the bath are isotropic random $k > 2$-body Majoranas fields, the Lyapunov exponent is positive for any strength of the coupling to the bath. Interestingly, this also applies to $q=2$ where the SYK is integrable which indicates that many-body quantum chaos can be induced by the environment. Moreover, for $q > 2$, where the unitary dynamics is quantum chaotic, and sufficiently large $k$, the Lyapunov exponent increases with the coupling to the bath. Explicit analytical results are obtained in the $q=2$ and large $q$ limits. Our results put forward an alternate route to induce and control the generation of scrambling in quantum many-body systems which is of potential relevance in the design of quantum information devices.