Charge and spin currents in a three-terminal mesoscopic ring

We theoretically investigate the charge and spin currents in a three-terminal mesoscopic ring in the presence of a uniform and nonuniform Rashba spin-orbit interaction (SOI). It is shown that a fully spin-polarized charge current and a pure spin current can be generated by tuning the probe voltages and/or the strength of the Rashba SOI. The charge and spin currents oscillate as the strength of the Rashba SOI increases induced by the spin quantum interference. The ratio of probe voltages oscillates synchronously with the pure spin current as the strength of the Rashba SOI increases in a nonuniform Rashba ring, while it remains constant in a uniform Rashba ring. We demonstrate theoretically that a three-terminal uniform Rashba ring can be used as a spin polarizer and/or spin flipper for different spin injections, and a nonuniform Rashba ring could allow us to detect the pure spin current electrically. (C) 2009 American Institute of Physics. [DOI 10.1063/1.3054322]

Structural, morphological, and magnetic characteristics of Cu-implanted nonpolar GaN films

Diluted magnetic nonpolar GaN:Cu films have been fabricated by implanting Cu ions into unintentionally doped nonpolar a-plane(1 1 (2) over bar 0) GaN films and a subsequent thermal annealing process. The structural, morphological and magnetic characteristics of the samples have been investigated by means of high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and superconducting quantum interference device (SQUID). The sample shows a clear ferromagnetism behavior at room temperature. It is significantly shown that with a Cu concentration as low as 0.75% the sample exhibits a saturation magnetization about 0.65 mu(B)/Cu atom. Moreover, the possible origin of the ferromagnetism for the sample was also discussed briefly. (C) 2009 Elsevier B. V. All rights reserved.

The impact of implantation dose on the characteristics of diluted-magnetic nonpolar GaN:Cu films

Diluted-magnetic nonpolar GaN:Cu films have been fabricated by implanting Cu ions into p-type nonpolar a-plane (1120) GaN films with a subsequent thermal annealing process. The impact of the implantation dose on the structural. morphological and magnetic characteristics of the samples have been investigated by means of high-resolution X-ray diffraction (HRXRD). atomic force microscopy (AFM), and superconducting quantum interference device (SQUID). The XRD and AFM analyses show that the structural and morphological characteristics of samples deteriorated with the increase of implantation dose. According to the SQUID analysis. obvious room-temperature ferromagnetic properties of samples were detected. Moreover, the saturation magnetization per Cu atom decreased as the implantation dose increased. (C) 2009 Elsevier B.V. All rights reserved.

Decoherence of two Josephson charge qubits coupled via sigma(x)sigma(x)-type coupling and exposed to sigma(x) noise

Decoherence properties of two Josephson charge qubits coupled via the sigma(x)sigma(x) type are investigated. Considering the special structure of this new design, the dissipative effects arising from the circuit impedance providing the fluxes for the qubits' superconducting quantum interference device loops coupled to the sigma(x) qubit variables are considered. The results show that the overall decoherence effects are significantly strong in this qubit design. It is found that the dissipative effects are stronger in the case of coupling to two uncorrelated baths than are found in the case of one common bath.

Ferromagnetism in Mn and Cr doped GaN by thermal diffusion

Doping of magnetic element Mn and Cr in GaN was achieved by thermal diffusion. The conductivity of the samples, which were all n-type, did not change significantly after the diffusion doping. X-ray diffraction measurements revealed no secondary phase in the samples. Experiments using superconducting quantum interference device (SQUID) showed that the samples were ferromagnetic at 5 and 300 K, implying the Curie temperature to be around or over 300 K, despite their n-type conductivity. (c) 2004 Elsevier B.V. All rights reserved.

A convenient way of determining the ferromagnetic transition temperature of metallic (Ga,Mn)As

We have studied magnetic and transport properties of insulating and metallic (Ga,Mn)As layers before and after annealing. A dramatic increase of the ferromagnetic transition temperature T-C by postgrowth annealing has been realized in both insulating and metallic (Ga,Mn)As. The as-grown insulating (Ga,Mn)As can be turned into metallic by the low-temperature annealing. For all the metallic (Ga,Mn)As, a characteristic feature in the temperature dependence of sheet resistance appears around T-C. This phenomenon may provide a simple and more convenient method to determine the T-C of metallic (Ga,Mn)As compared with superconducting quantum interference device (SQUID) measurement. Moreover, the T-C of the metallic (Ga,Mn)As obtained by this way is in good agreement with that measured by a SQUID magnetometer. (C) 2005 American Institute of Physics.

New type of Fano resonant tunneling via Anderson impurities in superlattice

The spectrum of differential tunneling conductance in Si-doped GaAs/AlAs superlattice is measured at low electric fields. The conductance spectra feature a zero-bias peak and a low-bias dip at low temperatures. By taking into account the quantum interference between tunneling paths via superlattice miniband and via Coulomb blockade levels of impurities, we theoretically show that such a peak-dip structure is attributed to a Fano resonance where the peak always appears at the zero bias and the line shape is essentially described by a new function \xi\/\xi\+1 with the asymmetry parameter q approximate to 0. As the temperature increases, the peak-dip structure fades out due to thermal fluctuations. Good agreement between experiment and theory enables us to distinguish the zero-bias resonance from the usual Kondo resonance.

Growth and magnetic properties of zincblende CrSb epilayers on relaxed and strained (In, Ga)As buffers

Zincblende CrSb (zb-CrSb) layers with room-temperature ferromagnetism have been grown on relaxed and strained (In,Ga)As buffer layers epitaxially prepared on (001) GaAs substrates by molecular-beam epitaxy. The structural characterizations of CrSb layers fabricated under the two cases are studied by using synchrotron grazing incidence x-ray diffraction (GID). The results of GID experiments indicate that no sign of second phase exists in all the zb-CrSb layers. Superconducting quantum interference device measurements demonstrate that the thickness of zb-CrSb layers grown on both relaxed and strained (In,Ga)As buffer layers can be increased to similar to 12 monolayers (similar to 3.6nm), compared to similar to 3 monolayers (similar to 1nm) on GaAs directly.

Structural and magnetic properties of GaN:Sm:Eu films fabricated by co-implantation method

Diluted-magnetic GaN:Sm:Eu films have been fabricated by co-implantation of Sm and Eu ions into c-plane (0001) GaN films and a subsequent annealing process. The structural, morphological and magnetic characteristics of the samples have been investigated by means of high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and superconducting quantum interference device (SQUID). The XRD and AFM analyses show that the annealing process can effectively recover the crystalline degradation caused by implantation. Compared with GaN:Sm films, more defects have been introduced into GaN:Sm:Eu films due to the Eu implantation process. According to the SQUID analysis, GaN:Sm:Eu films exhibit clear room-temperature ferromagnetism. Moreover, GaN:Sm:Eu films show a lower saturation magnetization (Ms) than GaN:Sm films.

A magnetic, luminescent and mesoporous core-shell structured composite material as drug carrier

In this paper, hydrothermal synthesized Fe3O4 microspheres have been encapsulated with nonporous silica and a further layer of ordered mesoporous silica through a simple sol-gel process. The surface of the outer silica shell was further functionalized by the deposition of YVO4:Eu3+ phosphors, realizing a sandwich structured material with mesoporous, magnetic and luminescent properties. The multifunctional system was used as drug carrier to investigate the storage and release properties using ibuprofen (IBU) as model drug by the surface modification. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), N-2 adsorption/desorption, photoluminescence (PL) spectra, and superconducting quantum interference device (SQUID) were used to characterized the samples.

Bifunctional magnetic-optical nanocomposites: Grafting lanthanide complex onto core-shell magnetic silica nanoarchitecture

Anew class of bifunctional architecture combining the useful functions of superparamagnetism and terbium complex luminescence into one material has been prepared via two main steps by a modified Stober method and the layer-by-layer (LbL) assembly technique. The obtained bifunctional nanocomposites exhibit superparamagnetic behavior, high fluorescence intensity, and color purity. The architecture has been characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-vis absorption and emission spectroscopy, X-ray diffraction, and superconducting quantum interference device (SQUID) magnetometry.

Hydrothermal synthesis of Fe and Mn doped SnO2 and its magnetic structures

The dilute magnetic semiconductor of Sn1-x-yMnxFeyO2 (0 <= x <= 0.10, 0 <= y <= 0.10) Were syhthesized with the hydrothermal method using SnCl4, Mn(CH3COO)(2) center dot 4H(2)O and FeCl3 center dot 6H(2)O as the raw materials. The structure, morphologies and magnetic properties of the sample were characterized via X-ray powder diffractometer(XRD), transmission electron microscopy(TEM), Raman spectrum and superconducting and quantum interference device(SQUIT), and Mossbeaur spectrum. No secondary phase was found in the XRD spectrum. The morphology of the samples is affected by the kind or the mount of transition metal. The local vibrating model-of Mn Positioned SnO2 sites was found in Raman spectrum. The measured magnetic results indicate that when x = 0.10, y = 0, the sample exhibits strong magnetization in low-temperature (5 K), but the magnetization decrease rapidly at room. temperature; In contrast, when x = 0, y = 0.1, the sample's magnetization and coercivity are both small, but being temperature independent. Mossbeaur spectra indicates that part of the Fe is ferromagnetic coupled, and the simulating results indicate that the ferromagnetic character is intrinsic.

Enhancing Kerr nonlinearity in an asymmetric double quantum well via Fano interference

We investigate the enhancement of Kerr nonlinearity in an asymmetric GaAs double quantum well via Fano interference, which is caused by tunneling from the excited subband to the continuum. In our structure, owing to Fano interference, the Kerr nonlinearity can be enhanced by appropriately choosing the values of the detunings and the intensity of the pump field, while cancel the linear and nonlinear absorptions.

Repeat-until-success distributed quantum computation by using single-photon interference at a beam splitter

A repeat-until-success (RUS) measurement-based scheme for the implementation of the distributed quantum computation by using single-photon interference at a 50:50 beam splitter is proposed. It is shown that the 50:50 beam splitter can naturally project a suitably encoded matter-photon state to either a desired entangling gate-operated state of the matter qubits or to their initial state when the photon is detected. The recurrence of the initial state permits us to implement the desired entangling gate in a RUS way. To implement a distributed quantum computation we suggest an encoding method by means of the effect of dipole-induced transparency proposed recently [E. Waks and J. Vuckovic, Phys. Rev. Lett. 96, 153601 (2006)]. The effects of the unfavorable factors on our scheme are also discussed.