title: Exploring chaos in the Dicke model using ground-state fidelity and Loschmidt echo.
abstract: We study the quantum critical behavior of the Dicke Hamiltonian with finite number of atoms and explore the signature of quantum chaos using measures like the ground-state fidelity and the Loschmidt echo and the time-averaged Loschmidt echo. We show that these quantities clearly point to the classically chaotic nature of the system in the superradiant (SR) phase. While the ground-state fidelity shows aperiodic oscillations as a function of the coupling strength, the echo shows aperiodic oscillations in time and decays rapidly when the system is in the SR phase. We clearly demonstrate how the time-averaged value of the echo already incorporates the information about the ground-state fidelity and stays much less than unity, indicating the classically chaotic nature of the model in the SR phase.
authors.affiliation: Department of Physics, Indian Institute of Technology, 208016, Kanpur.
authors.forename: Utso
authors.initials: U
authors.lastname: Bhattacharya
authors.affiliation: Department of Physics, Indian Institute of Technology, 208016, Kanpur.
authors.forename: Sayak
authors.initials: S
authors.lastname: Dasgupta
authors.affiliation: Department of Physics, Indian Institute of Technology, 208016, Kanpur.
authors.forename: Amit
authors.initials: A
authors.lastname: Dutta
mesh_terms: D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D011789:Quantum Theory; D013816:Thermodynamics