Floquet-engineered chiral-induced spin selectivity

The control of electron spin, which is crucial to the stability of matter, offers new possibilities for manipulating the properties of molecules and materials with potential applications in spintronics and chemical reactions. Recent experiments have demonstrated that electron transmission through chiral molecules depends on the electron spin orientation, a phenomenon known as chiral-induced spin selectivity (CISS). In this study, we show that CISS can be observed in achiral systems driven by an external circularly polarized laser field in the framework of Floquet engineering. By using the Floquet theory for a time-periodically driven system to investigate spin-dependent electron transport in a two-terminal setup, we demonstrate that the spin polarization can approach unity if the light intensity is sufficiently strong, the rate of dephasing is sufficiently small, and the average chemical potential of the two leads is within an appropriate range of values, which is narrow because of the high frequency of the laser field. To obtain a wider range of energies for large spin polarization, a combination of chiral molecules and light-matter interactions is considered and the spin polarization of electrons transported through a helical molecule driven by a laser field is evaluated.Comment: 7 pages, 3 figure

Some Recommendations for Preventing Child Sexual Abuse in Viet Nam

Crime prevention is an outreach measure to stop crime before it can occur. Prevention measures vary in different countries. Child sexual abuse is an issue of growing concern in Viet Nam. Child sexual abuse can cause serious damage to cognitive, social, and emotional development of a child. Effectively combatting this serious form of violence against children requires. Vietnamese government has initiated and supported services and policies that enhance children’s development, health and safety as well as advocated for policies and programs to help meet the basic needs of children and families. In this paper, the author intends to exam the child sexual abuse situation and crime prevention in the world and Vietnam

Direct and ultrafast probing of quantum many-body interactions through coherent two-dimensional spectroscopy: From weak- to strong-interaction regimes

Interactions between particles in quantum many-body systems play a crucial role in determining the electric, magnetic, optical, and thermal properties of the system. The recent progress in the laser-pulse technique has enabled the manipulations and measurements of physical properties on ultrafast timescales. Here we propose a method for the direct and ultrafast probing of quantum many-body interaction through coherent two-dimensional (2D) spectroscopy. Using a two-band fermionic Hubbard model for the minimum two-site lattice system, we find that the 2D spectrum of a noninteracting system contains only diagonal peaks; the interparticle interaction manifests itself in the emergence of off-diagonal peaks in the 2D spectrum before all the peaks coalesce into a single diagonal peak as the system approaches the strongly interacting limit. The evolution of the 2D spectrum as a function of the time delay between the second and third laser pulses can provide important information on the ultrafast time variation of the interaction

Finite temperature phase diagram of a spin-1 Bose gas

We formulate a self-consistent Hartree-Fock theory for a spin-1 Bose gas at finite temperature and apply it to characterizing the phase diagram. We find that spin coherence between thermal atoms in different magnetic sub-levels develops via coherent collisions with the condensed atoms, and is a crucial factor in determining the phase diagram. We develop analytical expressions to characterize the interaction and temperature dependent shifts of the phase boundaries.Comment: 11 pages, 5 figure