Search

The exciton properties of (Cd,Mn)Se-NrGO (nitrogen doped reduced graphene oxide) hybrid layered nanosheets have been studied in a magnetic field up to 10 T and compared to those of (Cd,Mn)Se nanosheets. The temperature dependent photoluminescence reveals the hybridization of inter-band exciton and intra-center Mn transition with enhancement of the binding energy of exciton-Mn hybridized state (80 meV with respect to 60 meV in (Cd,Mn)Se nanosheets) and increase of exciton—phonon coupling strength to 90 meV (with respect to 55 meV in (Cd,Mn)Se nanosheets). The circularly polarized magneto—photoluminescence at 2 K provides evidence for magnetic field induced exciton spin polarization and the realization of excitonic giant Zeeman splitting with geff as high as 165.4 ± 10.3, much larger than in the case of (Cd,Mn)Se nanosheets (63.9 ± 6.6), promising for implementation in spin active semiconductor devices. [ABSTRACT FROM AUTHOR]

We introduce a generalized Rashba coupling approximation to analytically solve confined two-dimensional electron systems with both the Rashba and Dresselhaus spin–orbit couplings in an external magnetic field. A solvable Hamiltonian is obtained by performing a simple change of basis, which has the same form as that with only Rashba coupling. Each Landau state becomes a new displaced-Fock state instead of the original Harmonic oscillator Fock state. Analytical energies are consistent with the numerical ones in a wide range of coupling strength even for a strong Zeeman splitting, exhibiting the validity of the analytical approximation. By using the eigenstates, spin polarization correctly displays a jump at the energy-level crossing point, where the corresponding spin conductance exhibits a pronounced resonant peak. As the component of the Dresselhaus coupling increases, the resonant point shifts to a smaller value of the magnetic field. In contrast to pure Rashba couplings, we find that the Dresselhaus coupling and Zeeman splittings tend to suppress the resonant spin Hall effect. Our method provides an easy-to-implement analytical treatment to two-dimensional electron gas systems with both types of spin–orbit couplings by applying a magnetic field. [ABSTRACT FROM AUTHOR]

We investigate theoretically the combination effect of an in-plane magnetic field and spin-orbit interactions (SOIs) on the spin and charge transport property of a quasi-one-dimensional quantum wire embedded in the (110) crystallographic plane. We find that the oscillations of the conductance induced by the SOIs become more significant and different for the spin-up and spin-down electrons in the presence of the in-plane magnetic field. The conductance exhibits a significant anisotropic behavior and electrons exhibit out-of-plane spin polarization which can be tuned by an in-plane magnetic field. These features offer us an efficient way to control SOI-induced spin transport using in-plane magnetic fields. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the spin polarization from two-dimensional hole gases (2DHG) formed in p–i–p GaAs/AlAs resonant tunnelling diodes (RTDs) under magnetic field parallel to the tunnel current. We have observed that the polarization degree from the quantum well (QW) and the 2DHG formed at the accumulation layer is highly voltage and light sensitive and exhibits a clear sign inversion. Our results indicate that the voltage dependence of the QW polarization degree is mainly due to an efficient hole-resonant tunnelling process through spin states of the QW. On the other hand, the voltage dependence of the 2DHG polarization degree seems to be dependent on the hole density which is controlled by the applied voltage across the RTDs. [ABSTRACT FROM AUTHOR]

We extend the covariance matrix description of atom–light quantum interfaces, originally developed for real and effective spin-1/2 atoms, to include ‘spin alignment’ degrees of freedom. This allows accurate modelling of optically probed spin-1 ensembles in arbitrary magnetic fields. We also include technical noise terms that are very common in experimental situations. These include magnetic field noise, variable atom number and the effect of magnetic field inhomogeneities. We demonstrate the validity of our extended model by comparing numerical simulations to a free–induction decay measurement of polarized 87Rb atoms in the f = 1 ground state. We qualitatively and quantitatively reproduce experimental results with no free parameters. The model can be easily extended to larger spin systems, and adapted to more complicated experimental situations. [ABSTRACT FROM AUTHOR]

Co/C granular films with 3-21% Co content are fabricated by facing-target magnetron sputtering. As the Co content increases, the isolated Co particles in the a-C matrix gradually connect with each other, and consequently the electrical transport of the Co/C films changes from insulating to metallic conduction. The insulating samples show spin-dependent negative magnetoresistance (MR), which is related to the alignment of the spins at the interface between Co particles and the carbon matrix. Interfacial spin polarization P0 is related to the amount of interfacial hybridization, which is influenced by the size of sp² carbon clusters in the a-C matrix. Metallic samples show the competition of negative MR and positive linear MR. Negative MR observed at low temperatures is caused by a weak localization effect and is suppressed when the magnetic field is above 15 kOe. Positive linear MR is observed at high fields and high temperatures, and could be explained by quantum electron-electron interaction theory. The magnetotransport properties in the Co/C films are significantly influenced by the configuration of Co particles and, consequently, the conduction regime rather than the size of sp2 carbon clusters in the a-C matrix. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a three-axis atomic magnetometer based on parametric oscillations, which can measure the three magnetic field components simultaneously and independently. A circularly polarized pump beam is applied to create the spin polarization, and another linearly polarized probe beam is used to detect the dynamics of the polarized spin under a magnetic field. With a closed-loop system to keep the magnetic field in resonance with the atoms, three components of magnetic field are measured by their feedback signals. We achieve a magnetometer sensitivity of 6 pT ()−1, 25 pT ()−1, and 60 pT ()−1 along three axes in the frequency range from 100 Hz to 1 kHz with a bandwidth better than 1 kHz under an unshielded environment. Furthermore, this magnetometer is free of optical modulation, which reduces the complexity of experimental setups. The methods we present here provide a prototype all-electrical three-axis atomic magnetometer. [ABSTRACT FROM AUTHOR]

A practical method to measure the spin polarization of optically pumped alkali atoms is demonstrated. In order to realize transverse measurement, the transverse spin component of spin-polarized alkali atoms is created by a rotating exciting magnetic field, and detected using the optical rotation of a near-resonant probe beam for realizing a high detection sensitivity. The dependency of the optical rotation on the spin polarization of 133Cs atoms is derived theoretically and verified experimentally. By changing the direction of the rotating magnetic field, we realize the transverse measurement of the spin polarization of 133Cs atoms in either ground-state hyperfine level. [ABSTRACT FROM AUTHOR]

We have investigated the polarization-resolved electroluminescence (EL) of a p–i–n GaAs/AlAs/InGaAs resonant tunneling diode (RTD) containing a GaMnAs (x  =  5%) spin injector under high magnetic fields. We demonstrate that under hole resonant tunneling condition, the GaMnAs contact acts as an efficient spin-polarized source for holes tunneling through the device. Polarization degrees up to 80% were observed in the device around the hole resonance at 2 K under 15 T. Our results could be valuable for improving the hole-spin injection in GaMnAs-based spintronic devices. [ABSTRACT FROM AUTHOR]

A proposal of an electrically controlled spin transistor in a helical magnetic field is presented. In the proposed device, the transistor action is driven by the Landau–Zener transitions that lead to a backscattering of spin polarized electrons and switching the transistor into the high-resistance state (off state). The on/off state of the transistor can be controlled by the all-electric means using Rashba spin–orbit coupling that can be tuned by the voltages applied to the side electrodes. [ABSTRACT FROM AUTHOR]

Spin polarization in an InAs quantum dot subjected to terahertz (THz) irradiation and external magnetic fields is theoretically discussed. Spin-polarized oscillations and spin polarization plateaus are obtained, depending on the relative magnitude between the external magnetic field strength and the THz photon energy. Furthermore, we show that the oscillation of spin polarization is also related to the THz irradiation amplitude. These features may be beneficial for low magnetic field detectors, ultrasensitive THz detectors or spin-selective applications. [ABSTRACT FROM AUTHOR]

The electron beam energy at the Hefei Light Source (HLS) in the National Synchrotron Radiation Laboratory is highly precisely calibrated by using the method of spin resonant depolarization for the first time. The spin tune and the beam energy are determined by sweeping the frequency of a radial rf stripline oscillating magnetic field to artificially excite a spin resonance and depolarize the beam. The resonance signal is recognized by observing the sudden change of the Touschek loss counting rate of the beam. The possible systematic errors of the experiment are presented and the accuracy of the calibrated energy is shown to be about 10−4. A series of measurements show that the energy stability of the machine is of the order of 9 × 10−3. [ABSTRACT FROM AUTHOR]

We study the generation of spin polarization in monolayer graphene in the presence of Rashba spin–orbit interaction (SOI) and a ferromagnetic (FM) stripe. It is shown that Rashba SOI alone can generate an in-plane (x–y plane) spin polarization, but a FM stripe with magnetization parallel to the current direction cannot generate any spin polarization. A combination of the Rashba SOI and the magnetic field of a FM stripe can increase the spin polarization to a value close to 100%, and the polarization components can be found along the x, y and z directions. The attainment of highly spin polarized current using the Rashba SOI and FM effect could have useful applications in the development of graphene spintronics. [ABSTRACT FROM AUTHOR]