We investigate signatures of the excited-state quantum phase transition in
the periodic dynamics of the Lipkin-Meshkov-Glick model and the Tavis-Cummings
model. In the thermodynamic limit, expectation values of observables in
eigenstates of the system can be calculated using classical trajectories.
Motivated by this, we suggest a method based on the time evolution of the
finite-size system, to find singularities in observables, which arise due to
the excited-state quantum phase transition.Comment: 9 pages, 3 figures, comments are welcom
We apply the time-delayed Pyragas control scheme to the dissipative Dicke model via a modulation of the atom-field-coupling. The feedback creates an infinite sequence of non-equilibrium phases with fixed points and limit cycles in the primary superradiant regime. We analyse this Hopf bifurcation scenario as a function of delay time and feedback strength and determine analytical conditions for the phase boundaries.( )z z z 0 0 = − = ⇒ = − J J J J J J˙˙˙˙.
Based on the Lindblad master equation approach we obtain a detailed microscopic model of photons in a dye-filled cavity, which features condensation of light. To this end we generalise a recent nonequilibrium approach of Kirton and Keeling such that the dye-mediated contribution to the photonphoton interaction in the light condensate is accessible due to an interplay of coherent and dissipative dynamics. We describe the steady-state properties of the system by analysing the resulting equations of motion of both photonic and matter degrees of freedom. In particular, we discuss the existence of two limiting cases for steady states: photon Bose-Einstein condensate and laser-like. In the former case, we determine the corresponding dimensionless photon-photon interaction strength by relying on realistic experimental data and find a good agreement with previous theoretical estimates. Furthermore, we investigate how the dimensionless interaction strength depends on the respective system parameters.
We theoretically investigate the role of dissipation in excited state quantum phase transitions (ESQPT) within the Lipkin-Meshkov-Glick model. Signatures of the ESQPT are directly visible in the complex spectrum of an effective Hamiltonian, whereas they get smeared out in the time-dependence of system observables. In the latter case, we show how delayed feedback control can be used to restore the visibility of the ESQPT signals. is the Lindblad-dissipator and = ˆĴ J J i . c 2 Note, that even the dissipative model still fulfils the conservation law + + = J J J 1 4, ( )
We consider a driven single mode Dicke-Hamiltonian coupled to a dissipative
zero-temperature bath. We derive the cumulant generating function for emitted
photons of this quantum-critical system by using a $P$-representation of the
master equation in the thermodynamic limit. This cumulant generating function
is shown to consist of two parts: a macroscopic component, which is Poissonian
in nature with characteristic rate proportional to the order parameter of the
system; and a part describing fluctuations which is non-trivial in form and
divergent around the quantum phase transition.Comment: 9 pages, 5 figure
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.