We study the nonequilibrium phase diagram and the dynamical phase transitions occurring during the prethermalization of nonintegrable quantum spin chains, subject to either quantum quenches or linear ramps of a relevant control parameter. We consider spin systems in which long-range ferromagnetic interactions compete with short-range, integrability-breaking terms. We capture the prethermal stages of the nonequilibrium evolution via a time-dependent spin-wave expansion at leading order in the spin-wave density. In order to access regimes with strong integrability breaking, instead, we perform numerical simulations based on the time-dependent variational principle with matrix product states. By investigating a large class of quantum spin models, we demonstrate that nonequilibrium fluctuations can significantly affect the dynamics near critical points of the phase diagram, resulting in a chaotic evolution of the collective order parameter, akin to the dynamics of a classical particle in a multiple-well potential subject to quantum friction. We also elucidate the signature of this novel dynamical phase on the time-dependent correlation functions of the local order parameter. We finally establish a connection with the notion of dynamical quantum phase transition associated with a possible nonanalytic behavior of the return probability amplitude, or Loschmidt echo, showing that the latter displays cusps whenever the order parameter vanishes during its real-time evolution.
|Titolo:||Impact of nonequilibrium fluctuations on prethermal dynamical phase transitions in long-range interacting spin chains|
|Autori:||Lerose, Alessio; Žunkovič, Bojan; Marino, Jamir; Gambassi, Andrea; Silva, Alessandro|
|Data di pubblicazione:||2019|
|Numero di Articolo:||045128|
|Digital Object Identifier (DOI):||10.1103/PhysRevB.99.045128|
|Appare nelle tipologie:||1.1 Journal article|