Zheng Yu-Jun

Quantum interference in a four-level system of a {sup 87}Rb atom: Effects of spontaneously generated coherence

In this work, the effects of quantum interference and spontaneously generated coherence (SGC) are theoretically analyzed in a four-level system of a {sup 87}Rb atom. For the effects of SGC, we find that a new kind of electromagnetically induced transparency channel can be induced due to destructive interference, and the nonlinear Kerr absorption can be coherently narrowed or eliminated under different strengths of the coupling and switching fields.

Autler—Townes splitting in photoelectron spectra of K2 molecule

We investigate Autler—Townes splitting in the photoelectron spectra of K2 molecule driven by pump-probe pulses via employing the time-dependent wave packet approach. It is found that the magnitude of Aulter—Townes splitting varies with the wavelength of the intense laser pulse. In particular, the phenomenon of Aulter—Townes splitting vanishes for the far-off resonance of the pump pulse. Also, the split peaks of Autler—Townes in the case of resonant pump pulse give us an approach to directly obtaining the transition dipole moment of a molecule.

Dynamics of vibrational chaos and entanglement in triatomic molecules: Lie algebraic model

In this paper, the dynamics of chaos and the entanglement in triatomic molecular vibrations are investigated. On the classical aspect, we study the chaotic trajectories in the phase space. We employ the linear entropy to examine the dynamical entanglement of the two bonds on the quantum aspect. The correspondence between the classical chaos and the quantum dynamical entanglement is also investigated. As an example, we apply our algebraic model to molecule H2O.

Evolution of Quantum Phase Space Distribution: a Trajectory-Density Approach

The trajectory-density method of a quantum system is developed by using local Koopman and Frobenius–Perron operators. We propose a new scheme of approximation from two sets of trajectory-density mixed equations. By examining the local generation and termination of trajectories, we show how they can be adopted to the propagation of negative values of the Wigner function even if it starts off positive everywhere.

Influences of excitation power and temperature on photoluminescence in phase-separated InGaN quantum wells

The photoluminescence (PL) properties of a green and blue light-emitting InGaN/GaN multiple quantum well structure with a strong phase separated into quasi-quantum dots (QDs) and an InGaN matrix in the InGaN epilayer are investigated. The excitation power dependences of QD-related green emissions (PD) and matrix-related blue emissions (PM) in the low excitation power range of the PL peak energy and line-width indicate that at 6 K both PM and PD are dominated by the combined action of Coulomb screening and localized state filling effect. However, at 300 K, PM is dominated by the non-radiative recombination of the carriers in the InGaN matrix, while PD is influenced by the carriers transferred from the shallower QDs to deeper QDs by tunnelling. This is consistent with the excitation power dependence of the PL efficiency for the emission.

Dynamical correlation between quantum entanglement and intramolecular energy in molecular vibrations: An algebraic approach *

The dynamical correlation between quantum entanglement and intramolecular energy in realistic molecular vibrations is explored using the Lie algebraic approach. The explicit expression of entanglement measurement can be achieved using algebraic operations. The common and different characteristics of dynamical entanglement in different molecular vibrations are also provided. The dynamical study of quantum entanglement and intramolecular energy in small molecular vibrations can be helpful for controlling the entanglement and further understanding the intramolecular dynamics.

Chaotic Dynamics of Triatomic Normal Mode Molecules

We investigate the chaotic dynamics of normal mode molecules from the classical point of view using the coupling Morse oscillators. New interesting phenomena of the fractured tori and the cross of tori on the Poincare section, which go against our traditional understanding, are found and investigated. Also, we find that the phenomenon of tori cross is a signature of the single bonds energy beyond the total vibrational energy. Finally, a method to improve this scarcity is proposed.

Theoretical study of highly vibrational states of nonlinear triatomic molecules using Lie algebraic approach

The vibrational excitations of bent triatomic molecules are studied by using Lie algebra. The RMS error of fitting 30 spectroscopic data is 1.66 cm−1 for SO2. The results show that the expansion of a molecular algebraic Hamiltonian can well describe the experimental data. And the total vibrational levels can be calculated using this Hamiltonian. At the same time, the potential energy surface can also be obtained with the algebraic Hamiltonian.

Photon Statistical Properties of Single Terrylene Molecules in P-Terphenyl Crystals

We consider the photon emission statistical properties of a single molecule under pump-probe field driving, using the generating function method. The first- and second-order moments of statistical quantities are presented. Derived from the first-order moment, the line shapes are in good agreement with the experimental results. Derived from the second-order moment, Mandels Q parameters show an obvious quantum effect of photon statistical distribution, i.e., the anti-bunching effect.

Photon counting statistics in single multi-level quantum system

We theoretically study the statistics of photon emission of a single multi-level quantum system by employing the generating functions approach developed recently. The generalized decay constants are included in a single multi-level quantum system with quasi-degenerated levels in this work although they are normally neglected in the absence of (quasi-)degeneracies in a multi-level quantum system within the rotating wave approximation. The quantum beats, the line shapes and the Mandels Q parameters, etc. are studied.