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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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Electronic Structures of Ge <sub/>2</sub> Sb <sub/>2</sub> Te <sub/>5</sub> /Co <sub/>2</sub> FeX (X: Al, Si) Interfaces for Phase Change Spintronics
摘要： Phase change materials (PCMs), such as Ge2Sb2Te5, are highly attractive in modern electronics and photonics. However, their spintronic applications remain largely unexplored. Here, we propose a tentative modality of phase change spintronic devices based on the ferromagnet/PCM/ferromagnet structure. The electrically tunable properties of a PCM interlayer give rise to new possibilities of manipulating spin transport through phase change, adding new functionalities and modes of operation to the spintronic devices. As the first step toward realizing such phase change spintronic devices, we calculate the electronic structures of the interfaces of c-Ge2Sb2Te5 and half-metallic ferromagnetic Co2FeX (X: Al, Si). The interfaces are found not to be genuine half-metallic, indicating room for improvement. The band alignments are largely determined by the termination of c-Ge2Sb2Te5. Two types of band alignments are found for c-Ge2Sb2Te5/Co2FeX interfaces. Considering c-Ge2Sb2Te5 as heavily p-type-doped, interfaces with Te termination are generally suitable such that they offer low contact resistance for hole injection from Co2FeX to c-Ge2Sb2Te5 in the majority spin channel; at the same time, they naturally form tunneling barriers, alleviating the degradation of spin injection efficiency because of occasional hole injection in the minority spin channel. This work provides important insights into this proposed phase change spintronic framework.
关键词： Spintronics,Electronic structures,Co2FeX,Interface,Phase change materials,Ge2Sb2Te5
更新于2025-09-23 15:21:01
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Light-induced magnetism in plasmonic gold nanoparticles
摘要： Strategies for the ultrafast optical control of magnetism have been a topic of intense research for several decades because of the potential impact in technologies such as magnetic memory, spintronics and quantum computation, as well as the opportunities for nonlinear optical control and modulation in applications such as optical isolation and non-reciprocity. Here we report experimental quantification of optically induced magnetization in plasmonic gold nanoparticles due to the inverse Faraday effect. The induced magnetic moment is large under typical ultrafast pulse excitation (<1014?W?m?2 peak intensity), with magnetization and demagnetization kinetics that are instantaneous within the subpicosecond time resolution of our study. Our results support a mechanism of coherent transfer of angular momentum from the optical field to the electron gas, and open the door to all-optical sub-wavelength strategies for optical isolation that do not require externally applied magnetic fields.
关键词： ultrafast optical control,quantum computation,inverse Faraday effect,spintronics,magnetic memory,plasmonic gold nanoparticles,light-induced magnetism
更新于2025-09-23 15:19:57
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Spin pumping and laser modulated inverse spin Hall effect in yttrium iron garnet/germanium heterojunctions
摘要： In this work, undoped semiconductors, germanium (Ge) and germanium tin (GeSn), were grown on ferrimagnetic insulator yttrium iron garnet (YIG) thin ?lms using ultra-high vacuum molecular beam epitaxy. The crystallinity of the structure was determined from x-ray diffraction and high-resolution transmission electron microscopy combined with energy dispersive x-ray spectroscopy. Both spin pumping and inverse spin Hall effects (ISHEs) of YIG/Ge and YIG/GeSn heterojunctions have been investigated with the help of broadband ferromagnetic resonance (FMR). We observe that the spin mixing conductances of YIG/Ge (60 nm) and YIG/GeSn (60 nm) are 5.4 (cid:2) 1018 m(cid:3)2 and 7.2 (cid:2) 1018 m(cid:3)2, respectively, responsible for giant spin current injection. Furthermore, it is found that spin pumping injects giant spin current from ferrimagnetic YIG into the Ge semiconductor. The infrared laser modulated ISHE was examined using heavy metal platinum as a spin current collector. Also, it has been noted that the variation in the power of laser irradiation signi?cantly changed the ISHE voltage of YIG/Ge/Pt spin junctions, saturated magnetization, FMR linewidth, and Gilbert damping parameter of YIG, which could be attributed to the laser-induced thermal effect. The outcomes from this study are promising for the development of Ge-based spintronic and magnonic devices.
关键词： germanium tin,magnonics,germanium,spin pumping,inverse spin Hall effect,yttrium iron garnet,spintronics
更新于2025-09-23 15:19:57
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Symmetry-breaking induced large piezoelectricity in Janus tellurene materials
摘要： Symmetry-breaking induced large piezoelectricity in Janus tellurene materials. Structural symmetry-breaking can lead to novel electronic and piezoelectric properties in two-dimensional (2D) materials. In this paper, we propose a 2D Janus tellurene (Te2Se) monolayer with asymmetric Se/Te surfaces and its derived multilayer structures. The band structure calculations show that the 2D Janus Te2Se monolayer is an indirect gap semiconductor, and the intrinsic mirror asymmetry combined with the spin–orbit coupling induces the Rashba spin splitting and the out-of-plane spin polarization. Moreover, the absence of both the inversion symmetry and out-of-plane mirror symmetry, together with flexible mechanical properties, results in large in-plane and out-of-plane piezoelectric coefficients that are valuable in 2D piezoelectric materials. Furthermore, the out-of-plane piezoelectric effects can exist in multilayer structures under different stacking sequences while the in-plane piezoelectric effect can only exist in some specific stacking patterns. The piezoelectric coefficients of the Janus Te2Se monolayer and multilayers exceed those of many Janus transition metal dichalcogenides and other well-known piezoelectric materials (e.g., a-quartz and wurtzite-AlN). The combination of the SOC-induced spin splitting and large piezoelectricity endows the Janus Te2Se structures with potential for applications in spintronics, flexible electronics and piezoelectric devices.
关键词： spintronics,2D materials,Janus tellurene,symmetry-breaking,piezoelectricity
更新于2025-09-19 17:15:36
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The electronic applications of stable diradicaloids: present and future
摘要： Organic molecules with unpaired electrons are intriguing for advanced applications in molecular electronics, spintronics and organic batteries, as well as other possible applications. Among them, diradicaloids have received growing attention due to the characteristic resonance structures between open-shell and closed-shell forms that lead to unique properties such as low energy bandgap and strong intermolecular spin–spin interaction. Therefore, in recent years, vast efforts have been devoted to investigate the synthesis, structure and fundamental properties of diradicaloids. However, the electronic applications of diradicaloids still remain in an early stage. Only a few diradicaloids have already found their place in electronic devices. In this perspective, we summarize the recent development of electronic applications of stable diradicaloids. The challenges and opportunities of stable diradicaloids for future electronic applications are also discussed.
关键词： spintronics,organic electronics,organic batteries,OFETs,NIR dyes,OPDs,diradicaloids,electronic applications
更新于2025-09-19 17:15:36
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Band offset modulation in Si-EuO heterostructures via controlled interface formation
摘要： Combining first-principles calculations and experiment, we investigate the atomic and electronic structure of the Si/EuO interface. We consider the thermodynamic stability of interface structures with different levels of oxidation to identify the most probable configuration. By comparing the calculated band alignment and core-level shifts with measured values, we validate the theoretically constructed interface model. We find that the band offset can be tuned by altering the relative energy positions of the Si and EuO conduction bands via interface oxidation, which can be used to tune this materials system for specific applications in spintronics.
关键词： XPS,band alignment,first-principles calculations,Si/EuO interface,spintronics
更新于2025-09-12 10:27:22
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Enhanced triplet state generation through radical pair intermediates in BODIPY-quantum dot complexes
摘要： Generation of triplet excited states through radical pair intermediates has been extensively studied in molecular complexes. Similar schemes remain rare in hybrid structures of quantum dot-organic molecules, despite intense recent interest of quantum dot sensitized triplet excited state generation. Herein, we demonstrate that the efficiency of the intersystem crossing from the singlet to the triplet state in boron dipyrromethene (BODIPY) can be enhanced in CdSe quantum dot-BODIPY complexes through a radical pair intermediate state consisting of an unpaired electron in the quantum dot conduction band and that in oxidized BODIPY. By transient absorption spectroscopy, we show that the excitation of BODIPY with 650 nm light leads to the formation of a charge separated state by electron transfer from BODIPY to CdSe (with a time constant of 6.33 ± 1.13 ns), competing with internal conversion to the ground state within BODIPY, and the radical pair state decays subsequently by back charge recombination to generate a triplet excited state (with a time constant of 158 ± 28 ns) or the ground state of BODIPY. The overall quantum efficiency of BODIPY triplet excited state generation was determined to be (27.2 ± 3.0)%. The findings of efficient triplet state formation and intermediate radical pair states in this hybrid system suggest that quantum dot-molecule complexes may be a promising platform for spintronics applications.
关键词： CdSe quantum dot,radical pair intermediates,transient absorption spectroscopy,intersystem crossing,spintronics,triplet excited states,BODIPY,quantum dot-organic molecules
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Petahertz Magnetization Dynamics
摘要： In contrast to conventional electronics, where only the charge of electrons is considered, spintronics is based on the utilization of both charge and spin. Due to this additional degree of freedom, spintronic devices can potentially provide higher processing speed or better energy efficiency. However, while sub-femtosecond control of the electronic properties of solids has previously been demonstrated, the lack of direct coupling between light and spin has limited the manipulation speed of magnetic properties to the few-tens-of-femtoseconds timescale. Here we introduce a technique able to follow the magnetic properties of a solid with attosecond resolution and demonstrate the direct sub-femtosecond all-optical manipulation of its spin degrees of freedom. We probe the time-evolution of the magnetic and electronic properties of solids and their coupling using a novel atto-XMCD scheme. In our experiment, a circularly polarized attosecond pulse (probe) (~310 as FWHM duration, centered at 66 eV corresponding to the M-edges of Nickel) is transmitted through a thin magnetized Nickel (Ni) film or Nickel-Platinum (Ni/Pt) multilayer sample. Reversing the magnetization direction allows to record the polarization dependent X-Ray absorption of Ni (X-Ray Magnetic Circular Dichroism, XMCD), which directly measures the magnetic moment of the Ni atoms. Dynamics are initiated by a carrier-envelope-phase stable sub-4 fs near-infrared electric laser field (pump). Coincidentally, attosecond transient absorption spectroscopy reveals changes of the electronic properties and gives a clear reference for the arrival of the laser pulse. Our results show an instantaneous response of both, charge and spin, to the laser pulse electric field in the Ni/Pt multilayer sample (Fig.1 a). The exceptionally fast demagnetization in the first 10 fs after laser excitation is the first experimental evidence for theoretically predicted optically induced spin transfer (OISTR): simultaneously with the charge transfer due to electronic excitation, the spin of excited electrons is transferred from the ferromagnetic (Ni) to the paramagnetic (Pt) material in the multilayer sample. This reduces the majority spin in Ni, inducing an instantaneous demagnetization of the ferromagnet. Fig. 1 b shows a reference measurement performed with a Ni film. As OISTR is not possible in pure Ni, no demagnetization happens during the pump laser pulse. To conclude, with our novel experimental scheme we demonstrate sub-femtosecond optical spin manipulation in matter. Access and control of the magnetic properties of solids on the attosecond time-scale paves the way towards spintronic devices operating at Petahertz clock rates.
关键词： Petahertz clock rates,X-Ray Magnetic Circular Dichroism,optically induced spin transfer,attosecond resolution,spintronics
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controlling Light Polarization from Helical Travelling-Wave Nanoantennas
摘要： Light polarization is a key factor of modern photonics. Tailoring surface plasmons (SPs) in anisotropically-shaped metallic nanostructures introduces the prospect of polarization control at small scale [1]. However, the resulting components remain much larger than the wavelength of light. Here, we present a travelling-wave helical plasmonic antenna (TW-HPA) that overcomes this limit [2]. Due to its non-resonant nature, it differs from existing helical plasmonic structures [3-5], thus extending the concept of travelling-wave helical antenna [6] to optics. Our TW-HPA consists of a narrow gold-coated wire wound up in a screw-like shape forming a tiny helix (Fig. 1a). The gold-coated wire sustains a cutoff-free axially symmetric travelling SPs [7], locally excited with the dipolar mode of a rectangular aperture nanoantenna right at the helix's pedestal. In the course of propagation, the plasmon wire mode acquires orbital angular momentum (OAM). Due to the sharp curvatures, the OAM of the SP mode match the spin angular momentum (SAM) of free-space propagating photons [8]. On the basis of this OAM-to-SAM transfer, individual TW-HPA can produce circularly polarized directional light on the subwavelength scale through a swirling-plasmon effect. Such TW-HPAs can then be closely packed to build micron scale arrangements of tiny circularly polarized light sources of desired handedness and tunable intensities, which could open new perspectives in a large panel of photonic applications requiring local addressing, such as detectors, displays, optomagnetic recording as well as quantum information. By optically coupling four TW-HPAs of opposite handedness (Fig.1b), we obtained a phase plate occupying a volume smaller than a cubic wavelength whose polarization properties have never previously been demonstrated. Switching between left and right circular polarizations (LCP and RCP) occurs when the incident linear polarization is rotated by an angle of 52°, instead of 90° as for standard quarter wave plates. Based on the spin-orbit interaction of light, our method is versatile, robust and leads to ultracompact plasmonic polarizers and unconventional phase plates. Taken as individual or coupled structures, TW-PHAs may pave the way towards highly integrated polarization-encoded optics, particularly for the generation and control of spin-encoded photon qubits in quantum information and optical spintronics.
关键词： Light polarization,orbital angular momentum,surface plasmons,circularly polarized light,optical spintronics,quantum information,spin angular momentum,helical travelling-wave nanoantennas
更新于2025-09-11 14:15:04