Difa Ye

Complex dynamics of correlated electrons in molecular double ionization by an ultrashort intense laser pulse

With a semiclassical quasistatic model we achieve insight into the complex dynamics of two correlated electrons under the combined influence of a two-center Coulomb potential and an intense laser field. The model calculation is able to reproduce experimental data of nitrogen molecules for a wide range of laser intensities from the tunneling to the over-the-barrier regime, and predicts a significant alignment effect on the ratio of double over single ion yield. The classical trajectory analysis allows us to unveil subcycle molecular double ionization dynamics.

Scaling Laws of the Two-Electron Sum-Energy Spectrum in Strong-Field Double Ionization

The sum-energy spectrum of two correlated electrons emitted in nonsequential strong-field double ionization (SFDI) of Ar was studied for intensities of 0.3 to 2×10^{14} W/cm^{2}. We find the mean sum energy, the maximum of the distributions as well as the high-energy tail of the scaled (to the ponderomotive energy) spectra increase with decreasing intensity below the recollision threshold (BRT). At higher intensities the spectra collapse into a single distribution. This behavior can be well explained within a semiclassical model providing clear evidence of the importance of multiple recollisions in the BRT regime. Here, ultrafast thermalization between both electrons is found occurring within three optical cycles only and leaving its clear footprint in the sum-energy spectra.

Intensity determination of superintense laser pulses via ionization fraction in the relativistic tunnelling regime

We address the quantum tunnelling (QT) effect in the scheme that retrieves the laser intensity via the ionization fraction of multiply charged ions proposed recently. Our discussions are based on both the analytical tunnelling rate formula and numerical calculations using the classical trajectory Monte Carlo + tunnelling (CTMC-T) technique. Both approaches show that the correction from the QT effect is up to one order of magnitude.

Applications of Nonlinear Adiabatic Evolution

In this chapter, we show selected applications of nonlinear adiabatic evolution in the geometric phase, in tunneling dynamics, and in quantum interference. We introduce the adiabatic geometric phase in a nonlinear coherent coupler and illustrate the nonlinear adiabatic tunneling with four cases, namely, Landau-Zener tunneling, Rosen-Zener tunneling, atom-molecule conversion, and composite adiabatic passage. Adiabatic nonlinear Ramsey interferometry is also discussed.

Introduction to Adiabatic Evolution

In this chapter, we introduce the basic concepts of adiabatic theory in both classical and quantum systems. We discuss classical adiabatic motion, introduce the concepts of the classical adiabatic invariant and the Hannay angle, and give three examples: the one-dimensional harmonic oscillator, the celestial two-body problem, and the Foucault pendulum. We describe quantum adiabatic evolution, present the quantum adiabatic theorem, and describe the adiabatic geometric phase (specifically, the Berry phase) and the virtual magnetic monopole. Five examples of quantum adiabatic evolution are shown. We also discuss classical-quantum correspondence.

Exotic Virtual Magnetic Monopoles and Fields

In this chapter, we introduce exotic virtual magnetic monopoles and fields; these phenomena are formed in two typical systems. The disk-shaped virtual magnetic field is found in a long-range interacting spin-half system with a mean-field description. The fractional virtual magnetic monopole occurs in a mean-field ultracold atom-molecule conversion system. The virtual magnetic monopole chain is demonstrated in a quantum many-body ultracold atom-molecule conversion system.

Nonlinear Adiabatic Evolution of Quantum Systems

In this chapter, we discuss the physical origins of the nonlinearity in quantum many-body systems. Based on the nonlinear Schrodinger equation, we introduce the adiabatic evolution of the quantum states, including both eigenstates and noneigenstates, and we introduce the nonlinear geometric phase acquired by an eigenstate during the adiabatic evolution. A nonlinear two-mode model for Bose-Einstein condensates (BECs) is used to demonstrate the nonlinear adiabatic theory.

Quantum-Classical Correspondence of an Interacting Bosonic Many-Body System

In this chapter, we discuss the adiabatic limit and the semiclassical limit, and we investigate the commutability between these two limits with a second-quantized two-mode bosonic model. We deduce the adiabatic Berry phase and the classical Hannay angle of an interacting bosonic many-body system , and we discuss the relationship between the quantum Berry phase, the classical Hannay angle, and the mean-field nonlinear geometric phase of this system.

Electron correlation dynamics of strong-field double ionization of atoms below recollision threshold

In recent combined experimental and theoretical study we have explored nonsequential double ionization of neon and argon atoms in the infrared light field (800nm) below the recollision threshold. We find that the two-electron correlation dynamics depends on atomic structure- side-by-side emission (correlation) for Ne and back-to-back emission (anticorrelation) for argon atoms. This can be explained theoretically within our three dimensional classical model calculation including tunnelling effect. The multiple recollisions as well as recollision-induced-excitation-tunnelling (RIET) effect dominate the anticorrelation of argon, whereas the laser-assisted instantaneous recollision dominates the correlation of neon.