



01253nas a2200145   4500008004100000245008900041210006900130260001500199490000800214520078100222100002101003700002501024700002101049856003701070       2019                        eng d00aInteraction-induced transition in the quantum chaotic dynamics of a disordered metal0 aInteractioninduced transition in the quantum chaotic dynamics of  c03/25/20190 v4053 a<p>We demonstrate that a weakly disordered metal with short-range interactions exhibits a transition in the quantum chaotic dynamics when changing the temperature or the interaction strength. For weak interactions, the system displays exponential growth of the out-of-time-ordered correlator (OTOC) of the current operator. The Lyapunov exponent of this growth is temperature-independent in the limit of vanishing interaction. With increasing the temperature or the interaction strength, the system undergoes a transition to a non-chaotic behaviour, for which the exponential growth of the OTOC is absent. We conjecture that the transition manifests itself in the quasiparticle energy-level statistics and also discuss ways of its explicit observation in cold-atom setups.</p>1 aSyzranov, S., V.1 aGorshkov, Alexey, V.1 aGalitski, V., M.  uhttps://arxiv.org/abs/1709.0929601571nas a2200133   4500008004100000245005700041210005400098260001500152520117000167100002101337700002501358700001701383856003701400       2017                        eng d00aOut-of-time-order correlators in finite open systems0 aOutoftimeorder correlators in finite open systems  c2017/04/273 a<p>We study out-of-time order correlators (OTOCs) of the form hA&circ;(t)B&circ;(0)C&circ;(t)D&circ;(0)i for a quantum system weakly coupled to a dissipative environment. Such an open system may serve as a model of, e.g., a small region in a disordered interacting medium coupled to the rest of this medium considered as an environment. We demonstrate that for a system with discrete energy levels the OTOC saturates exponentially &prop; Paie &minus;t/τi + const to a constant value at t &rarr; &infin;, in contrast with quantum-chaotic systems which exhibit exponential growth of OTOCs. Focussing on the case of a two-level system, we calculate microscopically the decay times τi and the value of the saturation constant. Because some OTOCs are immune to dephasing processes and some are not, such correlators may decay on two sets of parametrically different time scales related to inelastic transitions between the system levels and to pure dephasing processes, respectively. In the case of a classical environment, the evolution of the OTOC can be mapped onto the evolution of the density matrix of two systems coupled to the same dissipative environment.</p>1 aSyzranov, S., V.1 aGorshkov, Alexey, V.1 aGalitski, V.  uhttps://arxiv.org/abs/1704.08442