Light Induced Hall effect in semiconductors with spin-orbit coupling

We show that optically excited electrons by a circularly polarized light in a semiconductor with spin-orbit coupling subject to a weak electric field will carry a Hall current transverse to the electric field. This light induced Hall effect is a result of quantum interference of the light and the electric field, and can be viewed as a physical consequence of the spin current induced by the electric field. The light induced Hall conductance is calculated for the p-type GaAs bulk material, and the n-type and p-type quantum well structures.Comment: 5 pages, 3 figure

Theory for supersolid 4^4He

Although both vacancies and interstitial have relatively high activation energies in the normal solid, we propose that a lower energy bound state of a vacancy and an interstitial may facilitate vacancy condensation to give supersolidity in $^{4}$He . We use a phenomenological two-band boson lattice model to demonstrate this new mechanism and discuss the possible relevance to the recently observed superfluid-like, non-classical rotational inertial experiments of Kim and Chan in solid $^{4}$He. Some of our results may also be applicable to trapped bosons in optical lattices.Comment: 5 pages, 2 figure

Transverse electric current induced by optically injected spin current in cross-shaped InGaAs/InAlAs system

We examine electric response of a linearly polarized light normally shed on a cross-shaped quasi 2-dimensional InGaAs/InAlAs system with structure inversion asymmetry. The photo-excited conduction electrons carry a pure spin current with in-plane spin polarization due to the Rashba spin-orbit interaction. We use Landauer-B\"{u}ttiker formalism to show that this spin current induces two inward or outward transverse charge currents, which are observable in experiments. This effect may serve as an experimental probe of certain types of spin current.Comment: 5 pages, 3 figure

Dimethyl­ammonium bis­(4-methyl­morpholin-4-ium) tetra­chloridozincate

The title compound, (C2H8N)(C5H12NO)[ZnCl4], was synthesized by hydro­thermal reaction of ZnCl2 with 4-methyl­morpholine in a dimethyl­formamide solution. The asymmetric unit is composed of half a [ZnCl4]2− anion, half a 4-methyl­morpholin-4-ium cation and half a dimethyl­ammonium cation, all located on mirror planes parallel to ac. All the amine H atoms are involved in inter­molecular N—H⋯Cl hydrogen bonds, building up an infinite chain parallel to the c axis

Mott Insulator - Superfluid Transitions in a Two Band Model at Finite Temperature and Possible Application to Supersolid 4He

We study Mott insulator - superfluid transition in a two-band boson Hubbard model, which can be mapped onto a spin-1/2 XY model with spins coupled to an additional Ising degree of freedom. By using a modified mean field theory that include the effects of phase fluctuations, we show that the transition is first order at both zero and finite temperatures. On the Mott insulator side, there may be reentrance in phase transition. These features are consequences of the underlying transition between competing defect poor and defect rich phases. The relevance of the model and our results to supersolid 4He and cold bosonic atoms in optical lattices are discussed