Structural and electronic properties of phosphorus-doped titanium clusters: A DFT study

Small titanium-aluminum oxide clusters, TiAlOy− (y=1–3) and TiAl2Oy− (y=2–3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlOy− (y=1–3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08 eV based on their photoelectron spectra; those of TiAl2O2− and TiAl2O3− were estimated to be 1.17±0.08 and 2.2±0.1 eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO− is nearly linear with the O atom in the middle. That of TiAlO2− is a kite-shaped structure. TiAlO3− has a kite-shaped TiAlO2 unit with the third O atom attaching to the Ti atom. TiAl2O2− has two nearly degenerate Al–O–Ti–O–Al chain structures that can be considered as cis and trans forms. TiAl2O3− has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.

Photoelectron spectroscopy and density functional theory study of TiAlOy- (y=1-3) and TiAl2Oy- (y=2-3) clusters

By developing multiple-scale method combined with Wentzel–Kramer–Brillouin expansion, this paper analytically studies the modulating effect of weakly periodic potential on the dynamical properties of the Bose–Einstein condensates (BEC) trapped in harmonic magnetic traps. A black–grey soliton transition is observed in the BEC trapped in harmonic magnetic potential, due to the weakly periodic potential modulating effect. Meanwhile, it finds that with the slight increase of the weakly periodic potential strength, the velocity of the soliton decreases, while its width firstly decreases then increases, a minimum exists there. These results show that the amplitude, velocity, and width of matter solitons can be effectively managed by means of a weakly periodic potential.

http://iopscience.iop.org/article/10.1088/1674-1056/18/3/017/pdf

Controlling the motion of solitons in BEC by a weakly periodic potential

This paper solves exactly a set of fully quantized coupled equations describing the quantum dynamics of quantum spins mixing in spin-1 Bose?Einstein condensates by deriving the exact explicit analytical expressions for the evolution of creation and annihilation operators.

Exact analytical solution for quantum spins mixing in spin-1 Bose–Einstein condensates

In this paper, the extended Jaynes-Cummings-Dicke (JC-Dicke) model which describes a two-level atomic Bose-Einstein condensate (BEC) dispersive coupled to a high-finesse optical cavity is considered. The theoretical description of an effective Hamiltonian for BEC is introduced. The potential energy surface of the system is obtained from the direct product Heisenberg-Weyl (HW1) coherent states for the field and U(2) coherent states for the matter. Also, the variational energy is evaluated as the expectation value of the Hamiltonian for this state in the framework of mean-field approach. The quantum phase transitions (QPTs) and the Berry phase for this model are investigated numerically. We observed that the atom-atom interactions can strongly affect the quantum phase transition point. Furthermore, we noticed that the coherent atoms not only shift the phase transition point but also affect the macroscopic excitations in the superradiant phase. Moreover, it is found that the new phase transition occurs when the microwave amplitude changes. Some of the numerical results in this paper are agreement precisely with the results of our paper which has published in Int. J. Mod. Phys. B when we studied the same model using a different coherent state.

Evolution of Extended JC-Dicke Quantum Phase Transition with a Coupled Optical Cavity in Bose-Einstein Condensate System

Squeezing via the interaction between the cavity light field and the Bose–Einstein Condensate (BEC) in a double-well potential is considered within the context of the two-mode approximation. For the cavity light field initially in a coherent state, it is shown that by choosing appropriate parameters, quadrature squeezing of the cavity light field can be achieved and it exhibits periodic oscillation. We also study the case in which BEC is tuned to resonance by periodically modulating the trapping potential, and the quadrature squeezing of the cavity field exhibits periodic collapse and revival effect. Both analytic and numerical calculations are performed, and they are found to be in good agreement with each other. The result shows that the quantum statistical properties of the cavity light field can be manipulated by its coupling with the condensates in the double-well potential. On the other hand, dynamical properties of the condensates in the double-well potential will be reflected by the quadrature squeezing of the light field.

https://iopscience.iop.org/article/10.1088/1674-1056/17/5/012/pdf

Squeezing via coupling of Bose-Einstein condensates in a double-well potential with a cavity light field

The quadrature squeezing spectra in the resonance fluorescence of a V-type three-level atom driven by a coherent field and coupled to a single-mode cavity is investigated. For weak excitation, the fluorescence field exhibit squeezing in the out-of-phase quadrature. The coupling between the atom and the cavity mode can greatly enhance the squeezing centred at the laser frequency. More importantly, for strong excitation, under the effect of the cavity-atom coupling, the in-phase quadrature of fluorescence can exhibit two-mode squeezing at the two inner sideband frequencies. By working in the dressed-state representation and hiring secular approximation, we give an analytical explanation for the effect. The result shows, under appropriate conditions, the squeezing can be greatly enhanced by appropriately tuning the cavity resonant frequency.

Zhou Lu

Papers

Squeezing via coupling of Bose-Einstein condensates in a double-well potential with a cavity light field

Cavity-Induced Enhancement of Squeezing in Resonance Fluorescence of a V-Type Three-Level Atom