Spin-dependent Splitting Research Articles

Steering far-field spin-dependent splitting of light by inhomogeneous anisotropic media

An inhomogeneous anisotropic medium with specific structure geometry can apply the tunable spin-dependent geometrical phase to the light passing through the medium, and thus can be used to steer the spin-dependent splitting (SDS) of light. In this paper, we exemplify this inference by the q plate, an inhomogeneous anisotropic medium. It is demonstrated that when a linearly polarized light beam normally passes through a q plate, k-space SDS first occurs, and then the real-space SDS in the far-field focal plane of a converging lens is distinguishable. Interestingly, the SDS, described by the normalized Stokes parameter S3 shows a multilobe and rotatable splitting pattern with rotational symmetry. Further, by tailoring the structure geometry of the q plate and/or the incident polarization angle of light, the lobe number and the rotation angle both are tunable. Our result suggests that the q plate can serve as a potential device for manipulating the photon spin states and enable applications such as in nano-optics and quantum information.

Rashba-like spin degeneracy breaking in coupled thermal antenna lattices

Observation of a spin degeneracy breaking in thermal radiation emitted from an inhomogeneous anisotropic lattice composed of coupled antennas supporting surface waves is presented. The spin degeneracy removal is manifested by a spin-dependent momentum splitting of the radiative mode which resembles the Rashba effect. The spin split dispersion arises from the inversion asymmetry of the lattice. Our experiment confirms that the spatial rate of the inhomogeneity determines the degree of the spin- dependent momentum redirection. The influence of the inversion asymmetry on the dispersion was studied by comparing the results to those produced by homogeneous lattices and characterizing the behavior of the isolated thermal antennas.

Enhanced and switchable spin Hall effect of light near the Brewster angle on reflection

We reveal an enhanced and switchable spin Hall effect (SHE) of light near Brewster angle on reflection both theoretically and experimentally. The obtained spin-dependent splitting reaches 3200nm near Brewster angle, 50 times larger than the previous reported values in refraction. We find that the amplifying factor in week measurement is not a constant which is significantly different from that in refraction. As an analogy of SHE in electronic system, a switchable spin accumulation in SHE of light is detected. We were able to switch the direction of the spin accumulations by slightly adjusting the incident angle.

Enhancing or suppressing the spin Hall effect of light in layered nanostructures

The spin Hall effect (SHE) of light in layered nanostructures is investigated theoretically in this paper. A general propagation model describing the spin-dependent transverse splitting in the SHE of light is established from the viewpoint of classical electrodynamics. We show that the transverse displacement of wave-packet centroid can be tuned to either a negative or a positive value, or even zero, by just adjusting the structure parameters, suggesting that the SHE of light in layered nanostructures can be enhanced or suppressed in a desired way. The inherent secret behind this interesting phenomenon is the optical Fabry-Perot resonance in the layered nanostructure. We believe that these findings will open the possibility for developing new nano-photonic devices.

Antenna splitting functions for massive particles

An antenna shower is a parton shower in which the basic move is a color-coherent 2-to-3 parton splitting process. In this paper, we give compact forms for the spin-dependent antenna splitting functions involving massive partons of spin 0 and spin 1/2.

Geometric Doppler Effect: Spin-Split Dispersion of Thermal Radiation

A geometric Doppler effect manifested by a spin-split dispersion relation of thermal radiation is observed. A spin-dependent dispersion splitting was obtained in a structure consisting of a coupled thermal antenna array. The effect is due to a spin-orbit interaction resulting from the dynamics of the surface waves propagating along the structure whose local anisotropy axis is rotated in space. The observation of the spin-symmetry breaking in thermal radiation may be utilized for manipulation of spontaneous or stimulated emission.

Spin-bias driven magnetization reversal and nondestructive detection in a single molecular magnet

The magnetization reversal in a single molecular magnet (SMM) weakly coupled to an electrode with spin-dependent splitting of chemical potentials (spin bias) is theoretically investigated by means of the rate equation. A microscopic mechanism for the reversal is demonstrated by the avalanche dynamics at the reversal point. The magnetization as a function of the spin bias shows hysteresis loops tunable by the gate voltage and varying with temperature. The nondestructive measurement to the orientation of giant spin in SMM is presented by measuring the fully polarized electric current in the response to a small spin bias. For ${\text{Mn}}_{12}\text{ac}$ molecule, its small transverse anisotropy only slightly violates the results above. The situation when there is an angle between the easy axis of the SMM and the spin-quantization direction of the electrode is also studied.

An approach towards a constituent quark model on the light cone

We use the vacuum expectation value of a Wegner–Wilson loop representing a fast moving quark–antiquark pair to derive the light cone Hamiltonian for a q q ¯ meson. We solve the corresponding Schrödinger equation for various trial wave functions. The result shows how confinement determines the meson mass and wave function for valence quarks on the light cone. We also parametrize the effect of the spin-dependent splitting for a light meson and charmonium. The correct chiral-symmetry breaking pattern for the pion mass is obtained due to the self-energy of the quark.

Using spin bias to manipulate and measure spin in quantum dots

A double quantum dot coupled to electrodes with spin-dependent splitting of chemical potentials (spin bias) is investigated theoretically by means of the nonequilibrium Kyldysh Green's function formalism. By applying a large spin bias, the quantum spin in a quantum dot (dot 1) can be manipulated in a fully electrical manner. To noninvasively monitor the manipulation of the quantum spin in dot 1, it is proposed that the second quantum dot (dot 2) is weakly coupled to dot 1. In the presence of the exchange interaction between the two dots, the polarized spin in dot 1 behaves like an effective magnetic field and weakly polarizes the spin in the nearby quantum dot 2. By applying a very small spin bias to dot 2, the spin-dependent transport through dot 2 can be probed, allowing the spin polarization in dot 1 to be identified nondestructively. These two steps form a complete scheme to manipulate a trapped spin while permitting this manipulation to be monitored in the double-dot system using pure electric approaches.

Generalized Stern-Gerlach Effect for Chiral Molecules

The Stern-Gerlach effect is well known as spin-dependent splitting of a beam of atoms with magnetic moments by a magnetic-field gradient. Here, we show that an induced gauge potential may lead to a similar effect for chiral molecules. In the presence of three inhomogeneous light fields, the center of mass of a three-level chiral molecule is subject to an optically induced gauge potential, and the internal dynamics of the molecule can be described as an adiabatic evolution in the reduced pseudospin subspace of the two lowest energy levels. We demonstrate numerically that such an induced gauge potential can lead to observable pseudospin-dependent and chirality-dependent generalized Stern-Gerlach effects for mixed left- and right-handed chiral molecules under realistic conditions.

0.4 and 0.7 conductance anomalies in quantum point contacts

Self-consistent modelling based on local spin-density formalism is employed to calculate theconductance of quantum point contacts at finite temperatures. The total electrostaticpotential exhibits spin-dependent splitting, which persists at temperatures up to0.5 K and gives rise to the anomalies at 0.4 and 0.7 of the conductance quantum(2e2/h) occurring simultaneously in the absence of external magnetic fields.

Spin currents modulated by magnetic barriers in semiconductor nanowires

We present the properties of ballistic spin transport through magnetic barrier structures in semiconductor nanowires. Landauer's approach is adopted for the calculation of spin transport properties for various host material nanowires which are remarkably different from each other in the effective g-factor, g*. The spin polarization effect on the conductance of a nanowire is more efficient than that of a purely two-dimensional electron gas. Especially, when the bias increases the conductance of a nanowire with small g* is quantized as a step function and its spin dependence disappears. However, these behaviours are broken for a host material with large g* and the spin-dependent splitting appears in this case. We achieve the enhancement of the spin polarization effect on currents by increasing the number of magnetic barriers and we can finally obtain the perfect spin-polarized effect on the conductance.

Spin-dependent splitting of the tunnel conductivity peaks in the magnetic field for junctions involving CDW metals

Current–voltage characteristics for junctions involving normal and superconducting charge-density-wave metals in the magnetic field were calculated. Spin splitting was found both for symmetrical and non-symmetrical junctions.

Material dependence of spin transport modulated by magnetic barriers in semiconductor nano-wires

We present the properties of ballistic spin transport through magnetic barrier structures in semiconductor nano-wires. The Landauer's approach is adopted to calculation of the transmission probability and the conductance for various host material nano-wires which are different remarkably from each other in effective g-factors. A host material having small effective g-factor is quantized in the conductance and the spin-dependence is disappeared in it. Nevertheless this kind of behavior is broken for the host material having large effective g-factor and the spin-dependent splitting is shown.

Spin-resonant splitting in magnetically modulated semimagnetic semiconductor superlattices

We investigate spin-resonant splitting in magnetically modulated semimagnetic semiconductor superlattices by adopting tight-binding model and Green's function method under the influence of an external electric field. Spin-dependent resonant splitting features for both the transmission spectra and the current density spectra are discussed in more detail. Under no influence of the external electric field, the periodic nature of the spin superlattice leads to a regular profile of quantization in the transmission, which is composed of spin-dependent resonant bands separated by nonresonant gaps, where the resonant splitting rule of the transmission for spin-up case is exactly the same as that for spin-down case. The transmission resonances are drastically suppressed by the external electric field, the difference between resonant bands and nonresonant gaps is lessened and the transmission spectra are smoothed out. It is shown that splitting of the current density is more complex. In contrast with the transmission, the number of oscillations in the current density spectra has no simple direct correspondence to the number of unit cells and cannot be summarized in the simple rule.

Spectroscopy of doubly heavy baryons

Within a nonrelativistic quark model featuring a QCD-motivated Buchmüller-Tye potential, the mass spectra for the families of doubly heavy baryons are calculated by assuming the quark-diquark structure of the baryon wave functions and by taking into account spin-dependent splitting. Physically motivated evidence that, in the case where heavy quarks have identical flavors, quasistationary excited states may be formed in the heavy-diquark subsystem is analyzed.

Quarkonium mass splitting revisited: effects of closed mesonic channels

Modifications of the quarkonium mass spectrum induced by its virtual dissociation into a pair of heavy mesons are considered. Coupling between quark and mesonic channels results in noticeable corrections to spin-dependent mass splitting. In particular, accounting for the dissociation effect allows one to reproduce the observable hierarchy of mass splittings in the χ c , χ b and χ′ b multiplets.

The spin-dependent two-loop splitting functions

We present a complete description of the calculation of the spin-dependent next-to-leading order splitting functions. The calculation is performed in the light-cone gauge. We give results for different prescriptions for the Dirac matrix γ 5 in d = 4 − 2 ϵ dimensions and provide the link to the results in dimensional reduction.

Spin-resolved x-ray photoemission from ferromagnetic nickel.

Spin-resolved x-ray photoelectron-spectroscopy (SRXPS) studies of metallic-Ni core-level and valence-band photoemission are reported. Prominent spin polarizations are observed for all main components and satellites. A spin-dependent splitting of 0.38 eV is observed for the main Ni 3s component. The Ni 3s 6-eV satellite, as well as a secondary satellite located \ensuremath{\sim}14 eV from the main 3s peak, both display a nearly 100% majority-spin polarization. Analogous results are found for the Ni 2s level. The 6- and 14-eV satellites are assigned to final states derived from the $^{1}$G and $^{1}$S states, respectively, of a local \ensuremath{\sim}3${\mathit{d}}^{8}$ final-state valence configuration that is created by the shakeup of a \ensuremath{\downarrow}-spin 3d electron to states above ${\mathit{E}}_{\mathit{f}}$. The manifestation of these phenomena in SRXPS studies of the Ni valence band, 3p, 2${\mathit{p}}_{3/2}$, and 2${\mathit{p}}_{1/2}$ core levels is presented and discussed. The SRXPS data are consistent with an itinerant-electron extra-atomic screening model in Ni involving both unoccupied pure 3d states and unoccupied, unpolarized, and hybridized 3d-4sp states. Final-state occupation of these states following photexcitation leads qualitatively to a final-state Ni 3d valence configuration of \ensuremath{\sim}50% 3${\mathit{d}}^{9}$ and \ensuremath{\sim}50% 3${\mathit{d}}^{10}$. The 3${\mathit{d}}^{9}$ configuration is the origin of the satellite production in Ni.

Linearized Schrödinger equation for nuclear quadrupole surface vibrations.

The Schr\"odinger equation for nuclear quadruple surface vibrations is linearized with the consequence that a new spin degree of freedom appears in the wave function of the linearized equation. This spin is called collective spin and has a value of 3/2. The linearized Schr\"odinger equation for quadrupole vibrations is used for the description of certain collective aspects of even-odd $^{187,189,191}\mathrm{Ir}$ nuclei which have a spin 3/2 in their ground state. As a potential we use the \ensuremath{\gamma}-soft collective potential of the neighboring even-even nuclei, which is inserted into the linearized Schr\"odinger equation via a scalar coupling. This leads to a collective spin-dependent fine structure splitting of the energy levels governed by a collective SO(5) spin-orbit coupling and a correction to the kinetic energy. Further, we consider explicitly spin-dependent potentials which effectively describe the interaction of the valence nucleon with the core of the even-odd Ir nuclei. Already a simple collective SO(3) and SO(5) spin-orbit coupling is sufficient to reproduce the lowest excited states of the even-odd Ir nuclei.