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Embedded quantum dots in semiconductor nanostructures
摘要： In this work, we report the behavior of the tunneling current in a semiconductor nanostructure of (Ga, Al)As/GaAs which takes into account the behavior of the electrons and the Rashba’s spin orbit interaction in the presence of embedded quantum dots of di?erent geometries (lens, pyramid and ring) in voltage function, magnetic ?eld, and the di?erent values of the interaction spin orbit (π/2, π/4 and 3π/4). The results that were obtained show, that the intensity of the current presents appreciable changes when is changed the con?guration of the quantum dot as the intensities of external ?elds and spin polarization as well. All these internal and external e?ects that are studied in our model, signi?cantly modify the transport of information of the semiconductor nanostructure, our results show that the spin e?ects and the quantum dot con?guration contribute to the quantum memories e?ciency and the spin ?lter devices of actual use on nanoscience and nanotechnology.
关键词： quantum dots,Rashba’s spin orbit interaction,tunneling current,semiconductor nanostructures
更新于2025-09-11 14:15:04
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Simple model of the ground state and spin-orbital excitations of free and adsorbed Fe(II) phthalocyanine molecules
摘要： We investigate the ground state and low-energy spin-orbital excitations of a single iron(II) phthalocyanine molecule in isolation and on an oxidized Cu(110) surface. Considering the subspace spanned by the three lowest spin-triplet states of 3A2g and 3Eg symmetry, we diagonalize the Hamiltonian made of the anisotropic spin-orbit interaction and the ligand ?eld splitting (cid:2), de?ned as the energy difference between 3Eg and 3A2g. We ?nd that the ground state switches from a 3Eg-like state with large orbital moment and out-of-plane easy axis for (cid:2) < ?60 meV to a 3A2g-like singlet state with in-plane easy axis for (cid:2) > ?60 meV. The analysis of the ?rst excited states in the two regimes explains the zero-?eld splitting data reported for β-FePc as well as for FePc molecules adsorbed on an oxidized Cu(110) surface [N. Tsukahara et al., Phys. Rev. Lett. 102, 167203 (2009)]. Importantly, the calculated magnetic susceptibility obtained with the ab initio value (cid:2) = 93 meV compares remarkably well with the experimental data of β-FePc in the whole available temperature range of 1–300 K.
关键词： spin-orbital excitations,anisotropic spin-orbit interaction,oxidized Cu(110) surface,Fe(II) phthalocyanine,ligand ?eld splitting
更新于2025-09-10 09:29:36
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All-optical generation and ultrafast tuning of non-linear spin Hall current
摘要： Spin Hall effect, one of the cornerstones in spintronics refers to the emergence of an imbalance in the spin density transverse to a charge flow in a sample under voltage bias. This study points to a novel way for an ultrafast generation and tuning of a unidirectional nonlinear spin Hall current by means of subpicosecond laser pulses of optical vortices. When interacting with matter, the optical orbital angular momentum (OAM) carried by the vortex and quantified by its topological charge is transferred to the charge carriers. The residual spin-orbital coupling in the sample together with confinement effects allow exploiting the absorbed optical OAM for spatio-temporally controlling the spin channels. Both the non-linear spin Hall current and the dynamical spin Hall angle increase for a higher optical topological charge. The reason is the transfer of a higher amount of OAM and the enhancement of the effective spin-orbit interaction strength. No bias voltage is needed. We demonstrate that the spin Hall current can be all-optically generated in an open circuit geometry for ring-structured samples. These results follow from a full-fledged propagation of the spin-dependent quantum dynamics on a time-space grid coupled to the phononic environment. The findings point to a versatile and controllable tool for the ultrafast generation of spin accumulations with a variety of applications such as a source for ultrafast spin transfer torque and charge and spin current pulse emitter.
关键词： optical vortices,orbital angular momentum,Spin Hall effect,quantum rings,spin-orbit interaction,spintronics
更新于2025-09-10 09:29:36
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Interference Induced Enhancement of Magneto-Optical Effect in Pt/TbCo Hetero-Structured Films
摘要： Magnetic ?lms with a heavy metal layer show strong interfacial interaction of spin-orbit. Spin-orbit interaction is one of the key technologies for spintronics. In this paper, we measured magneto-optical Kerr spectra of Pt/TbCo hetero-structure ?lms on a thermally oxidized silicon substrate (0.3 mm); A: Pt (3 nm)/TbCo (6 nm)/Pt (3 nm), B: Si3N4 (10 nm)/TbCo (6 nm)/Pt (3 nm), and C: Pt (3 nm)/TbCo (6 nm)/Si3N4 (10 nm). Magneto-optical Kerr spectra of each sample were measured with a wavelength range of 300–700 nm, and were compared to the simulated spectra using the effective refractive index method. In the sample A, which has a symmetric structure, the simulated spectra are consistent with the measured ones. On the other hand, in the samples B and C, with an asymmetric structure, there are some differences between the simulated spectra and the measured ones in a lower photon energy region. This may be caused by interfacial effects of the spin-orbit interaction.
关键词： spin-orbit interaction,heavy metal,hetero structure,magnetooptical,TbCo
更新于2025-09-10 09:29:36
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Ultrafast mixing of radial and spin states driven by transient magnetic field in concentric double quantum ring in presence of Dresselhaus spin-orbit interaction
摘要： We consider the single- and two-electron systems confined in concentric double quantum ring (DQR) nanostructure which interacts with transient perpendicular magnetic field oscillating with THz frequency. For this purpose we find the solutions of time-dependent Schr?dinger equation utilizing Configuration Interaction method. We found that the transient magnetic field mixes the radial states, what trigger off the charge density oscillations in this direction, and these may be accompanied by spin oscillations, provided that a spin-orbit interaction (SOI) is involved. The pattern of density oscillations is more regular than those obtained for single- and two-electron spins what results from less complicated excitation energy spectra if SOI is not present in the system. The latter can be made more regular, i.e. the fluctuations of frequency and amplitude of spin oscillations shall be smaller, provided that the sign of the magnetic field at the begining of time evolution is chosen apropriately since not all energy levels corresponding to bJz = bLz (cid:0) bSz eigenstates have mirror symmetry in relation to B ! (cid:0)B transformation. Our outcomes indicate, that the combined effect of a few-picosecond-long magnetic pulse and SOI on electron spin in DQR would enable one to perform transition between spin-up and spin-down states within 2 ps.
关键词： spin-orbit interaction,quantum ring,magnetic pulse
更新于2025-09-10 09:29:36
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Three-dimensional modulations on the states of polarization of light fields
摘要： Light ?elds with spatially structured states of polarization (SoPs) are gathering increasing attention because of their potential applications from optical imaging and micromanipulation to classical and quantum communications. Meanwhile, the concepts within structured light ?elds have been extended and applied to acoustic, electron, and matter waves. In this article, we review recent developments of the SoP modulation of light ?elds, especially focusing on three-dimensional (3D) modulations on the SoPs of light ?elds. The recent progress and novel implementations based on 3D spin-dependent separation are discussed. Following the discussions to this physical phenomenon, we then describe recent developments on the vector ?elds with 3D structured SoP and intensity distributions, namely, 3D vector ?elds. The discussed phenomena inspire us to explore other structured light ?elds for the expansion of applications in biomedical, information science, quantum optics, and so on.
关键词： vector ?eld,phase,polarization,spin–orbit interaction
更新于2025-09-10 09:29:36
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || In or Out of Control? Electron Spin Polarization in Spin-Orbit-Influenced Systems
摘要： Spintronics is the key word to motivate studies of spin-polarized electronic states in solids and at surfaces or interfaces. The use of the electron spin in addition to the electron charge as information carrier—that is the goal for spintronics devices. The generation, manipulation, and detection of spin-polarized currents promise applications in information technology. However, in many materials, the electronic states are spin degenerate. The spin degeneracy may be lifted by two interactions: (i) exchange interaction in magnetically ordered materials, where the magnetization direction is the reference for the alignment of the spin magnetic moments. Independent of location and momentum, the electron spin magnetic moment is either aligned parallel to the magnetization direction (majority spin, lower in energy) or antiparallel to it (minority, higher in energy), leading to a spin-dependent energy splitting, called exchange splitting, of the bands; (ii) spin–orbit interaction (SOI), which is present in all materials but becomes relevant in systems with high atomic number. In ferromagnets, SOI enables hybridization between bands of different spin character, leading to spin–orbit-induced energy gaps, sometimes called spin hot spots in the band structure, which are held responsible for demagnetization processes. Furthermore, noncollinear magnetic structures such as skyrmions arise from SOI in ferromagnets. In nonferromagnets, SOI leads to energy splitting of bands with different total angular momentum j but not necessarily to spin-split bands. Only in systems, where inversion symmetry is broken, which is, for example, the case at surfaces, the bands exhibit a spin-dependent energy splitting, which itself depends on the momentum k. This so-called Rashba-type spin splitting was predicted for a two-dimensional electron gas and experimentally observed in surface states on heavy metal surfaces, for example, Au(111) and W(110). The spin-dependent splitting depends on the momentum parallel to the surface kk and reverses its sign upon a sign change of kk. As a consequence, no net magnetic moment is formed. In contrast to Rashba systems, where surface states become spin split by SOI, topological insulators such as Bi2Se3 exhibit so-called topological surface states (TSS), which only appear as a consequence of SOI. SOI is responsible for band inversion and formation of a gap, which is then closed by a surface state with Dirac-cone-like energy dispersion and characteristic spin texture.
关键词： Rashba-type spin splitting,Spin–orbit interaction,Dirac-cone-like energy dispersion,Topological surface state,Spintronics
更新于2025-09-09 09:28:46
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Numerical Simulation of the Transverse and Longitudinal Shifts of Reflected Beam
摘要： The effects of the spin-orbit interaction of light are observed at the wavelength scale and can be used in nanophotonics. The computer simulation of these effects is a necessary tool for creating devices, based on the spin-orbit interaction of light. We have developed a software package in Python to simulate two known effects, namely, transverse and longitudinal shifts of the center of gravity of beams at the total internal reflection. The package is based on the algorithm for the numerical solution of Maxwell's equations by the finite difference time domain method. We have used the modification of PML – UPML as absorbing boundary conditions. We simulated the refraction and total internal reflection of an electromagnetic wave at the plane interface between two transparent dielectrics and calculated the depth of penetration of a non-uniform electromagnetic wave, occurring at total internal reflection in the optically less dense medium. To test the software package, we have compared the reflection coefficients of the electromagnetic wave for the normal and oblique incidence on the plane interface, calculated by the simulation with the coefficients, obtained by Fresnel formulas for the s-polarization of the wave. We have numerically simulated the shifts of the center of gravity of beams of finite size in the plane of incidence and perpendicular to it, namely, the effects of Goos-H?nchen and Fedorov. The dependence of the direction of the transverse shift on the sign of the circular polarization of the incident beam was demonstrated. The dependence of the longitudinal shift on the direction of linear polarization is also demonstrated. It should be stressed that the developed software package can be applied for simulating of the longitudinal and transverse shifts in anisotropic media, media with optical activity, as well as thin films on the dielectric surface.
关键词： Goos-H?nchen effect,Fedorov-Imbert effect,spin-orbit interaction of light,FDTD,PML
更新于2025-09-04 15:30:14