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heterostructures: Examination of spin relaxation mechanism
摘要： The thickness, temperature, and composition studies of spin diffusion length (SDL) and spin Hall angle (SHA) are performed by measuring the spin Hall magnetoresistance in Pd1?xPtx/Y3Fe5O12 (=YIG) heterostructures. The SDL is found to be invariant to changes in the electron momentum relaxation time by varying the temperature, the normal metal (NM) thickness, or the alloy composition, while the SHA exhibits a nonmonotonic dependence on temperature. These findings suggest the appearance of D’yakonov-Perel’ spin relaxation mechanism and phonon skew scattering in our heterostructures that is associated with strong interfacial Rashba spin-orbit coupling (IRSOC). At last, we employ the ab initio calculations to quantify the IRSOC at the inversion-symmetry-broken NM/YIG interface.
关键词： spin diffusion length,spin relaxation mechanism,spin Hall angle,interfacial Rashba spin-orbit coupling,PdPt/YIG heterostructures
更新于2025-09-23 15:23:52
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Strongly anisotropic spin relaxation in the neutral silicon vacancy center in diamond
摘要： Color centers in diamond are a promising platform for quantum technologies, and understanding their interactions with the environment is crucial for these applications. We report a study of spin-lattice relaxation (T1) of the neutral charge state of the silicon vacancy center in diamond. Above 20 K, T1 decreases rapidly with a temperature-dependence characteristic of an Orbach process and is strongly anisotropic with respect to magnetic-field orientation. As the angle of the magnetic field is rotated relative to the symmetry axis of the defect, T1 is reduced by over three orders of magnitude. The electron spin coherence time (T2) follows the same temperature dependence but is drastically shorter than T1. We propose that these observations result from phonon-mediated transitions to a low-lying excited state that are spin conserving when the magnetic field is aligned with the defect axis, and we discuss likely candidates for this excited state.
关键词： anisotropy,spin relaxation,quantum technologies,diamond,silicon vacancy center,Orbach process
更新于2025-09-23 15:23:52
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Impact of transition metal ion doping on electron spin relaxation time in CdSe/ZnSe quantum dots
摘要： Theoretical calculations of spin relaxation time (SRT) of conduction electrons have been carried out considering the relaxation mediated by acoustic phonons using k.p perturbation theory and envelope function approximation in a transition metal doped II-VI semiconductor quantum dot under the strong con?nement regime. In this calculation, we are considering the transitions in the Zeeman sublevels arising due to magnetic impurity doping and applied magnetic ?eld in a Mn doped CdSe/ZnSe quantum dots. The occurrence of spin polarization switching at moderately low applied magnetic ?eld is established in Cd1(cid:1)xMnxSe/ZnSe quantum dots. The spin relaxation times have been found to be considerably longer with a higher dopant concentration in small magnetic ?elds (B < 2T) and at very low temperature (T < 50 K) regime. The results may help to demonstrate that, such small quantum dots can successfully be used as polarization switch in different spintronic nano-device.
关键词： Quantum dot,Electronic structure,Spin relaxation,Spintronics,Semiconductor
更新于2025-09-23 15:21:01
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Electrical control of a spin qubit in InSb nanowire quantum dots: Strongly suppressed spin relaxation in high magnetic field
摘要： In this paper we investigate the impact of gating potential and magnetic ?eld on phonon induced spin relaxation rate and the speed of the electrically driven single-qubit operations inside the InSb nanowire spin qubit. We show that a strong g factor and high magnetic ?eld strength lead to the prevailing in?uence of electron-phonon scattering due to deformation potential, considered irrelevant for materials with a weak g factor, like GaAs or Si/SiGe. In this regime we ?nd that spin relaxation between qubit states is signi?cantly suppressed due to the con?nement perpendicular to the nanowire axis. We also ?nd that maximization of the number of single-qubit operations that can be performed during the lifetime of the spin qubit requres single quantum dot gating potential.
关键词： spin qubit,spin relaxation,Rabi frequency,InSb nanowire,quantum dots
更新于2025-09-23 15:19:57
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Quantum Dot
摘要： Valley splitting is a key feature of silicon-based spin qubits. Quantum dots in Si/SixGe1?x heterostructures reportedly suffer from a relatively low valley splitting, limiting the operation temperature and the scalability of such qubit devices. Here, we demonstrate a robust and large valley splitting exceeding 200 μeV in a gate-defined single quantum dot, hosted in molecular-beam-epitaxy-grown 28Si/SixGe1?x. The valley splitting is monotonically and reproducibly tunable up to 15% by gate voltages, originating from a 6-nm lateral displacement of the quantum dot. We observe static spin relaxation times T1 > 1 s at low magnetic fields in our device containing an integrated nanomagnet. At higher magnetic fields, T1 is limited by the valley hotspot and by phonon noise coupling to intrinsic and artificial spin-orbit coupling, including phonon bottlenecking.
关键词： valley splitting,spin relaxation,spin qubits,molecular-beam-epitaxy,silicon,quantum dot
更新于2025-09-19 17:13:59
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Control of a spin qubit in a lateral GaAs quantum dot based on symmetry of gating potential
摘要： We study the influence of quantum dot symmetry on the Rabi frequency and phonon-induced spin relaxation rate in a single-electron GaAs spin qubit. We find that anisotropic dependence on the magnetic field direction is independent of the choice of the gating potential. Also, we discover that relative orientation of the quantum dot, with respect to the crystallographic frame, is relevant in systems with C1v, C2v, or Cn (n ≠ 4r) symmetry. To demonstrate the important impact of the gating potential shape on the spin qubit lifetime, we compare the effects of an infinite-wall equilateral triangle, square, and rectangular confinement with the known results for the harmonic potential. In the studied cases, enhanced spin qubit lifetime is revealed, reaching almost six orders of magnitude increase for the equilateral triangle gating.
关键词： spin qubit,GaAs,spin relaxation rate,Rabi frequency,quantum dot,gating potential
更新于2025-09-19 17:13:59
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Influence of bromide content on iodide migration in inverted MAPb(I <sub/>1?x</sub> Br <sub/>x</sub> ) <sub/>3</sub> perovskite solar cells
摘要： The effect of a systematic increase in the bromide content on mixed anion methyl ammonium lead halide, MAPb(I1?xBrx)3, perovskite solar cells is investigated. We show that at a critical bromide concentration (7.5%) we supress the slow impedance response from the cells. We link the changing impedance spectrum to a large increase in the activation energy for iodide motion. These results are corroborated by muon spin relaxation measurements, where we show that at the concentration of bromide typically used in high performance perovskite solar cells (17%) there is no sign of iodide motion in powders. Finally, we show JV curve hysteresis as a function of bromide content. The scan rate at which the maximum hysteresis index is observed does not change as the % Br is increased, leading us to conclude that the low frequency impedance response and the JV curve hysteresis are not caused by the same mobile ions.
关键词： bromide content,muon spin relaxation,perovskite solar cells,hysteresis,iodide migration,impedance spectroscopy
更新于2025-09-16 10:30:52
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Electron exchange energy of neutral donors inside a quantum well
摘要： We calculated the exchange energy of a pair of donor-bound electrons placed in the middle of an in?nite quantum well (QW). In order to obtain this energy for any interdonor distance and for any QW thickness, we have ?rst adapted to a QW the method developed by Gor’kov and Pitaevskii [L. P. Gor’kov and L. P. Pitaevskii, Dokl. Akad. Nauk SSSR 151, 822 (1963)] for a three-dimensional (3D) distribution of donors, and calculated the asymptotic form of the exchange energy. Second we have calculated the exchange energy of a “helium atom” in a QW; and third, inspired by the interpolation procedure proposed by Ponomarev et al. [I.V. Ponomarev et al., Phys. Rev. B 60, 5485 (1999)], we have obtained an interpolated expression for any interdonor distance. The obtained exchange energy is written in units of effective hartree, and the distance between the donors, as well as the width of the QW, are expressed in units of effective Bohr radius. We calculated the exchange energy for some commonly studied semiconductor materials, and discussed also the relationship between the exchange energy and the spin relaxation time for a donor concentration close to the insulator-metal transition.
关键词： insulator-metal transition,exchange energy,donor-bound electrons,spin relaxation time,quantum well
更新于2025-09-10 09:29:36
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Spin–orbit coupling in silicon for electrons bound to donors
摘要： Spin–orbit coupling (SOC) is fundamental to a wide range of phenomena in condensed matter, spanning from a renormalisation of the free-electron g-factor, to the formation of topological insulators, and Majorana Fermions. SOC has also profound implications in spin-based quantum information, where it is known to limit spin lifetimes (T1) in the inversion asymmetric semiconductors such as GaAs. However, for electrons in silicon—and in particular those bound to phosphorus donor qubits—SOC is usually regarded weak, allowing for spin lifetimes of minutes in the bulk. Surprisingly, however, in a nanoelectronic device donor spin lifetimes have only reached values of seconds. Here, we reconcile this difference by demonstrating that electric ?eld induced SOC can dominate spin relaxation of donor-bound electrons. Eliminating this lifetime-limiting effect by careful alignment of an external vector magnetic ?eld in an atomically engineered device, allows us to reach the bulk-limit of spin-relaxation times. Given the unexpected strength of SOC in the technologically relevant silicon platform, we anticipate that our results will stimulate future theoretical and experimental investigation of phenomena that rely on strong magnetoelectric coupling of atomically con?ned spins.
关键词： silicon,spin relaxation,Spin–orbit coupling,donor-bound electrons,quantum information
更新于2025-09-04 15:30:14