Quantum dynamics of an electron moving in coupled quartic and coupled double-well oscillators under intense laser fields

Abstract

The phenomenon of quantum chaos is investigated by employing the model of an electron moving in coupled nonlinear two-dimensional oscillators, namely, coupled quartic and coupled double-well oscillators, under intense laser fields. The unperturbed ground-state wavefunctions of the oscillators, obtained by solving the time-dependent Schrödinger equation (TDSE) in imaginary time, are evolved in real time by numerically solving the TDSE. Various signatures like autocorrelation function, distance function, quantum "phase space" volume, "phase space" trajectories and overlap integral (similar to quantum fidelity or Loschmidt echo) have been studied to diagnose quantum chaos in terms of sensitivity towards an initial state characterized by a mixture of quantum states (wavepacket), brought about by small changes in the Hamiltonian, rather than towards a "pure" quantum state (i.e., a single eigenstate). Other quantum dynamical aspects such as time-dependent probability density distributions as well as power spectra and high harmonic generation (HHG) spectra at different laser intensities have also been examined. In case of the coupled double-well oscillator, suppression of quantum chaos has been observed.