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Transition metal dichalcogenide (TMD) semiconductors are attracting much attention in research regarding device physics based on their unique properties that can be utilized in spintronics and valleytronics. Although current studies concentrate on the monolayer form due to the explicitly broken inversion symmetry and the direct band gap, bulk materials also hold the capability of carrying spin and valley current. In this study, we report the methodology to continuously control the spin-orbit coupling (SOC) strength of bulk TMDs Mo1-xWxSe2 by changing the atomic ratio between Mo and W. The results show the size of band splitting at the K valley the measure of the coupling strength is linearly proportional to the atomic ratio of Mo and W. Our results thus demonstrate how to precisely tune the SOC coupling strength, and the collected information of which can serve as a reference for future applications of bulk TMDs.

Magnetic field-free, nonvolatile magnetic memory with low power consumption is highly desired in information technology. In this work, we report a current-controllable alignment of magnetic domain walls in a single layer La0.67Sr0.33MnO3 thin film with the threshold current density of 2 × 105 A/cm2 at room temperature. The vector relationship between current directions and domain-wall orientations indicates the dominant role of spin-orbit torque without an assistance of external magnetic field. Meanwhile, significant planar Hall resistances can be readout in a nonvolatile way before and after the domain-wall reorientation. A domain-wall-based magnetic random-access memory (DW-MRAM) prototype device has been proposed.

Current-induced magnetization switching by spin-orbit torque generated in heavy metals offers an enticing realm for energy-efficient memory and logic devices. The spin Hall efficiency is a key parameter in describing the generation of spin current. Recent findings have reported enhancement of spin Hall efficiency by mechanical strain, but its origin remains elusive. Here, we demonstrate a 45% increase in spin Hall efficiency in the platinum/cobalt (Pt/Co) bilayer, of which 78% of the enhancement was preserved even after the strain was removed. Spin transparency and X-ray magnetic circular dichroism revealed that the enhancement was attributed to a bulk effect in the Pt layer. This was further confirmed by the linear relationship between the spin Hall efficiency and resistivity, which indicates an increase in skew-scattering. These findings shed light on the origin of enhancement and are promising in shaping future utilization of mechanical strain for energy-efficient devices. Agency for Science, Technology and Research (A*STAR) Economic Development Board (EDB) National Research Foundation (NRF) Submitted/Accepted version This work is supported by an Industry-IHL Partnership Program (NRF2015-IIP001-001) and an EDB-IPP (RCA − 17/284) grant. This work is also supported by the RIE2020 ASTAR AME IAF-ICP grant (No. I1801E0030). W.Z. and P.K.J.W. acknowledge financial support by the Fundamental Research Funds for the Central Universities.

Complex oxide heterointerfaces provide a platform to manipulate spin-orbit coupling under the broken inversion symmetry. Moreover, their weak antilocalization (WAL) effect displays quantum coherent behavior due to the strong spin-orbit coupling. Herein, we break through the limitation of lattice mismatch at ReAlO3/STO (Re = La, Pr, Nd, Sm, and Gd) heterointerfaces and obtain their two-dimensional electric gas (2DEG) by spin coating. The effect of different Re elements in the resulting quantum corrections on the conductivity is investigated. It is observed that the conductivity of heterointerfaces is reduced with larger atomic numbers due to the ionization potential of Re elements. Moreover, magnetoresistance (MR) measurements in a perpendicular or a parallel field distinctly uncover strong Rashba spin-orbit coupling (SOC) in ReAO/STO samples besides SAO/STO (Re = Sm) and GAO/STO (Re = Gd), and the effective fields of the SOC (Hso) gradually increase from LAO/STO (Re = La, Hso = 0.82 T) to NAO/STO (Re = Nd, Hso = 1.37 T) at 2 K. The competition between SOC scattering and inelastic scattering is revealed through a temperature-dependence study of MR, and the WAL-weak localization transition is at about 6 K. Furthermore, unambiguous results of the Kondo effect, nonlinear Hall, hysteresis loop, and Rashba SOC suggest the coexistence of WAL at the PAO/STO (Re = Pr) heterointerface with exchange coupling between the localized magnetic moment and the itinerant electron. These results pave a unique route for the exploration of spin-polarized 2DEGs at oxide heterointerfaces.

Harnessing the unique features of topological materials for the development of a new generation of topological based devices is a challenge of paramount importance. Using Floquet scattering theory combined with atomistic models we study the interplay between laser illumination, spin and topology in a two-dimensional material with spin-orbit coupling. Starting from a topological phase, we show how laser illumination can selectively disrupt the topological edge states depending on their spin. This is manifested by the generation of pure spin currents and spin-polarized charge photocurrents under linearly and circularly polarized laser-illumination, respectively. Our results open a path for the generation and control of spin-polarized photocurrents., 7 pages, 4 figures

Chemical modification can effectively control the quantum spin Hall (QSH) state by changing the lattice constant or topological phase transition. We functionalized ultraflat stanene with hydrogen and halogens on a single side (s-SnX) and both sides (b-SnX). It was found that the buckled heights of the neighboring Sn atoms for s-SnX were still zero, while b-SnX changed into a buckled structure, which is consistent with previous studies. In this work, the electronic and topological properties of s-SnX (X = H, F, Cl, Br, I) were mainly studied based on first-principles calculations. We predicted that s-SnF, s-SnCl and s-SnBr would be topological insulators (TIs). It was found that the band structures of s-SnF, s-SnCl, s-SnBr have s-p band inversions and semimetal-to-semiconductor transitions considering spin orbit coupling (SOC) with the largest band gap of 0.25 eV. The edge bands of calculating the edge states cross linearly, and the numbers of edge bands passing through the zero energy level between –X and Γ point are odd, indicating that s-SnF, s-SnCl and s-SnBr are TIs. Ultraflat stanene functionalized by hydrogen and halogen atoms can effectively control QSH states. It is proved that functionalization provides more choices for topological insulator materials and topological device applications.

The temperature dependences of resistance for the p-type conductivity solid solution silicon–germanium whiskers doped by boron with concentration of 1 × 1018 cm−3 were investigated in the temperature range of 4.2–300 K and under the uniaxial compressive strain till − 3 × 10–3 rel. un. We studied the strain influence, which was caused on a spin–orbit splitting in the valence band spectrum. As an outcome, the spin–orbit splitting energies for both light and heavy holes were discovered based on the k–p method. The strain-induced effects of solid solution Si0.2Ge0.8 whiskers were studied at low temperatures. Found giant piezoresistive effect at helium temperature gives opportunity to create the supersensitive strain gages on the basis of silicon–germanium whiskers with doping concentration in the vicinity to the metal–insulator transition. The mechanical sensor operating at helium temperature and deformation range of 5 × 10–4–1.3 × 10–3 rel. un. was designed with the sensitive element Si0.2Ge0.8 whiskers doped to concentration 1 × 1018 cm−3.

We investigate the effects of a time-dependent gate voltage on a spin–orbit interaction (SOI) coupled interacting double quantum dot (DQD) system. For a tunnel coupled detuned DQD with two interact...

Recently, two-dimensional (2D) materials have been studied due to its unique properties and potentials for electronic devices. Tin Selenide (SnSe) is a promising material to be developed in many fields by identifying its electronic structure. In this study, we investigate the effect of layer-dependent electronic properties of SnSe using first-principles calculations based on density functional theory (DFT). We firstly optimized layer dependent of the lattice constant and atomic distortion and then calculate the electronic structure-related parameter including band structure and density of electron (DOS). We find that the calculated band gap decreases with increasing the layers of SnSe which is not dependent on fully relativistic calculation by turning spin orbit coupling (SOC). However, we identify substantial spin splitting in the band structure under the presence of the SOC, making this multilayer is promising for spintronics.

The electronic structure and magnetic properties of the binary alloys CoxNb1-x have been investigated by means of the density functional theory (DFT), implemented in the WIEN2k code. The exchange and correlation potential was processed by different approximations GGA and GGA + U including the spin orbit coupling (SOC) effect. The inclusion of SOC shows a very weak effect on the cobalt magnetic moments, However, Hubbard's correction induces a considerable improvement in the magnetic moment of the Co element. The calculation shows that the density of state (DOS) of the Co element is dominated by the 3d band state contribution, whereas the Nb state density is dominated by the 4d band states. Hybridization between the 3d-(Co) and 4d-(Nb) states in Co-Nb alloys reduces the spin polarization of 3d-(Co) states, resulting in a strong decrease in magnetic moment. The magnetic moment of the studied alloys is not only influenced by cobalt atom concentration but it is also influenced by the crystalline phase.

Through a combination of density functional theory calculations and cluster-expansion formalism, the effect of the configuration of the transition metal atoms and spin-orbit coupling on the thermodynamic stability and electronic bandgap of monolayer 2H-Mo1-xWxS2 is investigated. Our investigation reveals that, in spite of exhibiting a weak ordering tendency of Mo and W atoms at 0 K, monolayer 2H-Mo1-xWxS2 is thermodynamically stable as a single-phase random solid solution across the entire composition range at temperatures higher than 45 K. The spin-orbit coupling effect, induced mainly by W atoms, is found to have a minimal impact on the mixing thermodynamics of Mo and W atoms in monolayer 2H-Mo1-xWxS2; however, it significantly induces change in the electronic bandgap of the monolayer solid solution. We find that the band-gap energies of ordered and disordered solid solutions of monolayer 2H-Mo1-xWxS2 do not follow Vegard's law. In addition, the degree of the SOC-induced change in band-gap energy of monolayer 2H-Mo1-xWxS2 solid solutions not only depends on the Mo and W contents, but for a given alloy composition it is also affected by the configuration of the Mo and W atoms. This poses a challenge of fine-tuning the bandgap of monolayer 2H-Mo1-xWxS2 in practice just by varying the contents of Mo and W.

International audience; The results of recent theoretical studies of features of superconducting states in hybrid structures whose properties are significantly determined by the spin–orbit effects have been reported. The two main phenomena appearing in such systems in the presence of additional spin splitting caused either by the Zeeman effect in a magnetic field or by the exchange field: (i) the generation of spontaneous currents and (ii) the appearance of topologically nontrivial superconducting phases. It has been shown that the spin–orbit coupling can be a key mechanism that allows implementing new inhomogeneous phase structures, in particular, the so-called “phase batteries.” The effect of geometric factors on the properties of topologically nontrivial superconducting states has been analyzed. New types of topological transitions in vortex states of Majorana wires have been proposed.

The realization of multifunctional two-dimensional (2D) materials is fundamentally intriguing, such as the combination of piezoelectricity with a topological insulating phase or ferromagnetism. In this work, a Janus monolayer SrAlGaSe4 is built from the 2D MA2Z4 family with dynamic, mechanical and thermal stabilities, which is piezoelectric due to the lack of inversion symmetry. The unstrained SrAlGaSe4 monolayer is a narrow gap normal insulator (NI) with spin orbital coupling (SOC). However, the NI to topological insulator (TI) phase transition can be induced by biaxial strain, and a piezoelectric quantum spin Hall insulator (PQSHI) can be achieved. More excitingly, the phase transformation point is only about 1.01 tensile strain, and the nontrivial band topology can hold until the considered 1.16 tensile strain. Moreover, Rashba spin splitting in the conduction bands can exist in a PQSHI due to the absence of a horizontal mirror symmetry and the presence of SOC. For monolayer SrAlGaSe4, both in-plane and very weak out-of-plane piezoelectric polarizations can be induced with the application of uniaxial strain. The calculated piezoelectric strain coefficients d11 and d31 of monolayer SrAlGaSe4 are −1.865 pm V−1 and −0.068 pm V−1 at 1.06 tensile strain as a representative TI. In fact, many PQSHIs can be realized from the 2D MA2Z4 family. To confirm that, similar to SrAlGaSe4, the coexistence of piezoelectricity and topological orders can be realized by applying strain (about 1.04 tensile strain) in the CaAlGaSe4 monolayer. This study suggests that Janus monolayer SrAlGaSe4 is a pure 2D system for a PQSHI, enabling future studies exploring the interplay between piezoelectricity and topological order, which can lead to novel applications in electronics and spintronics.

Here, we used collinear and noncollinear density functional theory (DFT) methods to explore the interfacial properties of two heterojunctions between a fullerene (C60 and C70) and the MAPbI3(110) surface. Methodologically, consideration of the spin-orbit interaction has been proven to be required to obtain accurate energy-level alignment and interfacial carrier dynamics between fullerenes and perovskites in hybrid perovskite solar cells including heavy atoms (such as Pb atoms). Both heterojunctions are predicted to be the same type-II heterojunction, but the interfacial electron transfer process from MAPbI3 to C60 is completely distinct from that to C70. In the former, the interfacial electron transfer is slow because of the associated large energy gap, and the excited electrons are thus trapped in MAPbI3 for a while. In contrast, in the latter, the smaller energy gap induces ultrafast electron transfer from MAPbI3 to C70. These points are further supported by DFT-based nonadiabatic dynamics simulations including the spin-orbit coupling (SOC) effects. These gained insights could help rationally design superior fullerene-perovskite interfaces to achieve high power conversion efficiencies of fullerene-perovskite solar cells.

The concept of gauge fields plays a significant role in many areas of physics from particle physics and cosmology to condensed matter systems, where gauge potentials are a natural consequence of electromagnetic fields acting on charged particles and are of central importance in topological states of matter. Here, we report on the experimental realization of a synthetic non-Abelian gauge field for photons in a honeycomb microcavity lattice. We show that the effective magnetic field associated with TE-TM splitting has the symmetry of Dresselhaus spin-orbit interaction around Dirac points in the dispersion, and can be regarded as an SU(2) gauge field. The symmetry of the field is revealed in the optical spin Hall effect (OSHE), where under resonant excitation of the Dirac points precession of the photon pseudospin around the field direction leads to the formation of two spin domains. Furthermore, we observe that the Dresselhaus field changes its sign in the same Dirac valley on switching from s to p bands in good agreement with the tight binding modelling. Our work demonstrating a non-Abelian gauge field for light on the microscale paves the way towards manipulation of photons via spin on a chip., Original version submitted for peer review

Our work reveals a class of three-dimensional materials whose main features are dominated by d-orbital states. Their unique properties are derived from the low-energy states t2g. Without spin-orbital coupling (SOC), we find a triple degenerate point with a quadratic dispersion, demonstrated by an effective Hamiltonian. When SOC is included, the sign of SOC could determine the topological phases of materials: a negative SOC contributes a Dirac semimetal phase with a quadratic energy dispersion, whereas a positive SOC leads to a strong topological insulator phase. There exist clear surface states for the corresponding topological phases. Very interestingly, by application of a triaxial strain, the sequence of bands can be exchanged, as do the topological phases. In particular, there exists a 6-fold degenerate point under a critical strain. Furthermore, we use a uniaxial compressive/tensile strain, changing the quadratic Dirac point into a linear Dirac/strong topological insulator phase.

In this article, elpasolite perovskites, Cs2NaMCl6 (M = In, Tl, Sb, Bi), are investigated using density functional theory (DFT). Structural properties like lattice constants and bond lengths are in agreement with the available experimental data. Electronic properties are calculated by several DFT exchange-correlation approximations, and it is found that a modified Becke–Johnson (mBJ) approximation along with the inclusion of spin orbit coupling (SOC) gives the most promising results. The M-site cation decides the nature of the band gap; i.e. direct band gaps are obtained for group IIIA elements (In, Tl), and indirect band gaps are experiential for group VA elements (Sb, Bi). Narrow discrete energy bands are observed in the valence and conduction bands, which make these compounds suitable for scintillation applications. SOC induces splitting of Bi/Sb p orbitals in the conduction band and reduces the band gaps of these double perovskite halides. Obtained values of mechanical parameters confirm that these compounds are ductile and anisotropic. Optical properties, i.e. dielectric functions, energy loss function and refractive index, are also calculated, and interesting variations are found which can play a important role in scintillation and other optoelectronic applications of these materials.

In linear optics, the angular momentum of light can be easily manipulated through the optical spin-orbit interaction (SOI) in structured media such as liquid crystals, metasurfaces, and forked gratings. Similarly, metasurfaces can be used to generate nonlinear optical beams with both custom-defined spin angular momentum (SAM) and orbital angular momentum (OAM) states. However, it has been limited to a low-order process in which only a Gaussian-shaped fundamental wave is used. In this work, the high-order nonlinear optical SOI effect on metasurfaces is demonstrated through the generation of multiple angular momentum states in nonlinear waves. This is achieved by exploiting the degrees of freedom provided by both the SAM and the OAM states of the fundamental wave (FW) and the topological charges of the plasmonic metasurfaces. The mechanism of both intrinsic and extrinsic contributions to the OAM of the nonlinear waves is revealed. High-order nonlinear SOI on metasurfaces offers new opportunities for realizing ultracompact nonlinear vortex beams.

The interaction between a quantum particle’s spin angular momentum1 and its orbital angular momentum2 is ubiquitous in nature. In optics, the spin–orbit optical phenomenon is closely related with the light–matter interaction3 and has been of great interest4,5. With the development of laser technology6, the high-power and ultrafast light sources now serve as a crucial tool in revealing the behaviour of matter under extreme conditions. A comprehensive knowledge of the spin–orbit interaction for intense light is of utmost importance. Here, we report the in situ modulation and visualization of the optical orbital-to-spin conversion in the strong-field regime. We show that, through manipulating the morphology of femtosecond cylindrical vector vortex pulses7 by a slit, the photon’s orbital angular momentum can be controllably transformed into spin after focusing. By employing a strong-field ionization experiment, the orbital-to-spin conversion can be imaged and measured through the photoelectron momentum distributions. Such detection and consequent control of the spin–orbit dynamics of intense laser fields has implications for controlling photoelectron holography and coherent extreme-ultraviolet radiation8. Sculpting and focusing femtosecond cylindrical vector vortex pulses by a slit allows the controllable transformation of the photon’s orbital angular momentum into spin angular momentum, which can be characterized in situ by a strong-field ionization experiment.

Two dimensional (2D) materials are currently gaining a lot of interest due to excellent properties that are different from their bulk structures. Single and few-layered of Transition metal dichalcogenides (TMDCs) have a bandgap that ranges between 1-2 eV, which is used for FET devices or any optoelectronic devices. Within TMDCs, a ton of consideration is focused on Molybdenum Disulfide (MoS2) because of its promising band gap-tuning and transition between direct to indirect bandgap properties relies upon its thickness. The density functional theory (DFT) calculations with different functionals and spin-orbit coupling (SOC) parameters were carried out to study the electronic properties of bulk and monolayer MoS2. The addition of SOC brought about a noteworthy change in the profile of the band energy, explicitly the splitting of the valence band maximum (VBM) into two sub-bands. The indirect bandgap in bulk MoS2 ranges from 1.17- 1.71eV and that of the monolayer bandgap was 1.6 – 1.71eV. The calculated parameters were compared to the obtained experimental and theoretical results. The obtained density of states (DOS) can be used in explaining the nature of bandgap in both the bulk and monolayer MoS2. These electronic characteristics are important for applications in material devices and energy-saving applications

We investigate the crossed Andreev reflection (CAR) through a quantum dot (QD) coupled to topological superconducting single-stranded DNA (ssDNA). It is found that the topological nontrivial states appear in the QD due to leakage of the Majorana zero mode. Majorana zero mode can be identified by measuring the CAR. This device can be used as a Majorana zero mode detector that relies on the system parameters, such as the spin orbit coupling, the twist angle, molecular length. A high efficiency Cooper pair splitter can be realized by regulating the magnitude and direction of the gate voltage. In additions, the signature of CAR is robust against the Coulomb blockade and the disorder induced by distinct amino acids. This work provides an alternative method for detection of Majorana zero mode in ssDNA.

A magnetic field is generally considered to be incompatible with superconductivity as it tends to spin-polarize electrons and breaks apart the opposite-spin singlet superconducting Cooper pairs. Here, an experimental phenomenon is observed that an intriguing reemergent superconductivity evolves from a conventional superconductivity undergoing a hump-like intermediate phase with a finite electric resistance in the van der Waals heterointerface of layered NbSe2 and CrCl3 flakes. This phenomenon merely occurred when the applied magnetic field is parallel to the sample plane and perpendicular to the electric current direction as compared to the reference sample of a NbSe2 thin flake. The strong anisotropy of the reemergent superconducting phase is pointed to the nature of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state driven by the strong interfacial spin-orbit coupling between NbSe2 and CrCl3 layers. The theoretical picture of FFLO state nodes induced by Josephson vortices collectively pinning is presented for well understanding the experimental observation of the reemergent superconductivity. This finding sheds light on an opportunity to search for the exotic FFLO state in the van der Waals heterostructures with strong interfacial spin-orbit coupling., 24

Piezo-phototronic effect is a fundamental effect of semiconductors lacking of central symmetry with geometries from one-dimensional (1D) nanowire to 3D bulk. Here, we present that the piezo-phototr...

In the high spin–orbit-coupled Sr2IrO4, the high sensitivity of the ground state to the details of the local lattice structure shows a large potential for the manipulation of the functional properties by inducing local lattice distortions. We use epitaxial strain to modify the Ir–O bond geometry in Sr2IrO4 and perform momentum-dependent resonant inelastic X-ray scattering (RIXS) at the metal and at the ligand sites to unveil the response of the low-energy elementary excitations. We observe that the pseudospin-wave dispersion for tensile-strained Sr2IrO4 films displays large softening along the [h,0] direction, while along the [h,h] direction it shows hardening. This evolution reveals a renormalization of the magnetic interactions caused by a strain-driven cross-over from anisotropic to isotropic interactions between the magnetic moments. Moreover, we detect dispersive electron–hole pair excitations which shift to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. This behavior shows an intimate coupling between charge excitations and lattice distortions in Sr2IrO4, originating from the modified hopping elements between the t2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr2IrO4 and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin–orbit coupling., Proceedings of the National Academy of Sciences of the United States of America, 117 (40), ISSN:0027-8424, ISSN:1091-6490

Photonic skyrmions have applications in many areas, including the vectorial and chiral optics, optical manipulation, deep-subwavelength imaging and nanometrology. Much effort has been focused on the experimental characterization of photonic skyrmions. Here, we give an insight into the spin and orbital features of photonic skyrmions constructed by the p-polarized and s-polarized surface waves at an interface with various electric and magnetic properties by analyzing the continuity of chirality, energy flow and momentum densities through the electric and magnetic interface. The continuity of chirality density indicates that the photonic skyrmion has a property of the optical transverse spin. Most importantly, the continuity of energy flow and momentum densities results in four spin–orbit interaction quantities, which indicate the gradient of electric polarizability or permeability governs the spin–orbit interaction of photonic skyrmions and leads to the discontinuity and even the reversal of spin orientation through the optical interface. Our investigations on the spin–orbit properties of photonic skyrmions, which can give rise to the spin-dependent force and topological unidirectional transportation, is thorough and can be extended to other classical wave, such as acoustic and fluid waves. The findings help in understanding the spin–orbit feature of photonic topological texture and in constructing further optical manipulation, sensing, quantum and topological techniques.

Summary Advances in thermoelectrics are motivated by the innovation of thermoelectric theories. The Rashba effect, spin-dependent band splitting, paves a new path to enhance thermoelectric performance. Herein, we investigate the Rashba effect in GeTe, in which the rhombohedral distortion provides a unique handle to examine the mechanism of the Rashba effect for tuning thermoelectric properties. Fundamentally, we discover that the Rashba effect originates from the specific atomic site displacement. Experimentally, Sn-doped GeTe has a strong Rashba effect and yields an ultra-high power factor, meanwhile additional Sb alloying effectively tunes the carrier concentration. Moreover, microstructure characterizations reveal that the co-existence of grain boundaries, nanoprecipitates, and stacking faults significantly reinforces phonon scatterings and leads to an ultra-low lattice thermal conductivity. Finally, a high figure of merit is achieved in Ge1−x−ySnxSbyTe. The demonstrated benchmark figure of merit originated from the Rashba effect can provide a promising arena for enhancing thermoelectric performance in wide materials.

The interactions of photonic spin angular momentum and orbital angular momentum, i.e., the spin-orbit coupling in focused beams, evanescent waves or artificial photonic structures, have attracted intensive investigations for the unusual fundamental phenomena in physics and potential applications in optical and quantum systems. It is of fundamental importance to enhance performance of spin-orbit coupling in optics. Here, we demonstrate a titanium dioxide (TiO2)–based all-dielectric metasurface exhibiting a high efficient control of photonic spin Hall effect (PSHE) in a transmissive configuration. This metasurface can achieve high-efficiency symmetric spin-dependent trajectory propagation due to the spin-dependent Pancharatnam-Berry phase. The as-formed metadevices with high-aspect-ratio TiO2 nanofins are able to realize (86%, measured at 514 nm) and broadband PSHEs in visible regime. Our results provide useful insights on high-efficiency metasurfaces with versatile functionalities in visible regime.

Hydrogen-terminated diamond possesses an intriguing p-type surface conductivity which is induced via thermodynamically driven electron transfer from the diamond surface into surface acceptors such as atmospheric adsorbates, a process called surface transfer doping. High electron affinity transition metal oxides (TMOs) including MoO3 and V2O5 have been shown to be highly effective solid-state surface acceptors for diamond, giving rise to a sub-surface two-dimensional (2D) hole layer with metallic conduction. In this work, low temperature magnetotransport is used as a tool to show the presence of a Rashba-type spin-orbit interaction with a high spin-orbit coupling of 19.9 meV for MoO3 doping and 22.9 meV for V2O5 doping, respectively, through the observation of a transition in the phase-coherent backscattering transport from weak localization to weak antilocalization at low temperature. Surface transfer doping of diamond with TMOs provides a 2D hole system with spin-orbit coupling that is over two times larger than that reported for diamond surfaces with atmospheric acceptors, opening up possibilities to study and engineer spin transport in a carbon material system.

Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to a singlet excited state, plays a key role in a wide range of photochemical applications. Understanding and predicting the kinetics of such processes in vastly different molecular structures would facilitate the rational material design. Here, we demonstrate a theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet–triplet crossing seam involving a higher-lying triplet excited state where the semi-classical Marcus parabola is no longer valid. The present model explains the counterintuitive substitution effects of bromine on the RISC rate constants of previously unknown molecules, providing a predictive tool for material design., Understanding and predicting the kinetics of reverse intersystem crossing (RISC) facilitates the design of materials. Here, the authors demonstrate a theoretical expression that reproduces experimental RISC rate constants ranging over five orders of magnitude in selected molecules.

Ce1–xPrxO2−δ (CPO) is a prominent mixed ionic and electronic conductor known for its unique oxygen storage capacity due to two redox-active cations. The oxygen storage properties depend on both the...

The results of electrically detected magnetic resonance (EDMR) experiments on organic Schottky barrier diode based on regioregular poly(3-hexylthiophene-2,5-diyl) [P3HT] are presented. The existenc...

Lead halide perovskites (LHPs) exhibit large spin-orbit coupling (SOC), leading to only twofold-degenerate valence and conduction bands and therefore allowing for efficient optical orientation. This makes them ideal materials to study charge carrier spins. With this study we elucidate the spin dynamics of photoexcited charge carriers and the underlying spin relaxation mechanisms in CsPbI3 nanocrystals by employing time-resolved differential transmission spectroscopy (DTS). We find that the photoinduced spin polarization significantly diminishes during thermalization and cooling toward the energetically favorable band edge. Temperature-dependent DTS reveals a decay in spin polarization that is more than 1 order of magnitude faster at room temperature (3 ps) than at cryogenic temperatures (32 ps). We propose that spin relaxation of free charge carriers in large-SOC materials like LHPs occurs as a result of carrier-phonon scattering, as described by the Elliott-Yafet mechanism.

The effects of lead positions and lead-ring coupling regimes are investigated for spin-related transport through a two-dimensional network of quantum nanorings (2DNQRs) considering Rashba spin–orbit interaction (RSOI) and magnetic flux. A matrix representation of the transmission and reflection coefficients through a single ring connected to the arbitrary number of leads has been introduced. As a specific example of 2DNQRs, the conductance, spin polarization and system efficiency are obtained via a triangular network of quantum rings (TNQRs). TNQRs are completely opaque or transparent versus RSOI strength and wave vector (k) of the incident electron. The periodicity of these functions along the k axis depends on the lead positions and is independent of lead-ring coupling. Also, the symmetric geometry and strong lead-ring coupling regime significantly improve the performance of the system as a multipurpose spintronic device (i.e., a perfect spin filter, spin splitter, spin switching, Stern–Gerlach device and an electronic switching device).

CaTe exhibits Dirac-like linear dispersion in a simple cubic CsCl-type structure which is stable above pressure of 33 GPa. In the present paper, we have studied all the alkaline earth metal chalcogenides to check for the possibility of a structural transition pressure (Ps) below 33 GPa and also exhibiting Dirac-like linear dispersions as in CaTe. Our results show that a larger cation or anion increases the unit cell volume and lowers the Ps and vice versa. Although the Ps can be lowered by isoelectronic substitution, the Dirac-like electronic band dispersion around Ps is exhibited only by SrTe at 17 GPa which is almost half the Ps for CaTe. Interestingly, our study finds that in absence of spin-orbit interaction all studied alkaline chalcogenides exhibit Dirac-like dispersions at pressures ranging from 17 GPa for SrTe to 650 GPa for CaS, whereas a few retain Dirac-like dispersion even under the effect of spin-orbit interaction.

The spectral and luminescent properties of 21-thia- and 21,23-dithia-5,10,15,20-tetraphenylporphyrin were studied in solutions at 293 K. The origin of the spectral shifts of the absorption bands upon heterosubstitution was discussed based on the Gouterman four-orbital model. Fluorescence quenching of the heteroporphyrins was shown to be due to an internal heavy-atom effect of the thiophene-ring heteroatom.

We report on observation of superconducting current and AC Josephson effect in mesa-heterostructures with the interfaces comprised spin-singlet superconducting electrodes, coupled by a barrier made from strontium iridate, a material with the strong spin-orbit interaction. The superconducting critical current density was jC ≈ 0.3 A/cm2 at T = 4.2 K for mesa-heterostructures with d = 7 nm and jC ≈ 4 A/cm2 for d = 5 nm. The zero-bias conductance peak has been observed due to low energy states originated at Sr2IrO4/YBa2Cu3Ox interface. Under influence of weak magnetic field the critical current IC(H) dependences showed Fraunhofer-like pattern indicating absence of pinholes, supported also by oscillating with microwave power Shapiro steps. Fiske resonance steps with voltage positions deviated from the ordinary ones were registered for mesas with d = 5 nm.

Selective-area epitaxy provides a path toward high crystal quality, scalable, complex nanowire networks. These high-quality networks could be used in topological quantum computing as well as in ultrafast photodetection schemes. Control of the carrier density and mean free path in these devices is key for all of these applications. Factors that affect the mean free path include scattering by surfaces, donors, defects, and impurities. Here, we demonstrate how to reduce donor scattering in InGaAs nanowire networks by adopting a remote-doping strategy. Low-temperature magnetotransport measurements indicate weak anti-localization—a signature of strong spin–orbit interaction—across a nanowire Y-junction. This work serves as a blueprint for achieving remotely doped, ultraclean, and scalable nanowire networks for quantum technologies.

Mixed dimensional van der Waals heterostructures (MD-vdWhs) open a huge potential to fabricate novel devices based on numerous metamaterials with superior magnetotransport properties. In conventional vdWhs, a variety of two dimensional (2D) layers has been stacked together to demonstrate vdWhs with phenomenal functionalities. However, fabricating 2D materials and their vdWhs over large areas with excellent magnetoresistance (MR) characteristics remains a major challenge. Graphene foam (GF), a 3D form of Dirac graphene continued to gather much attention for magnetotransport applications due to its gram-scale/cost effective production and better magnetoresistance properties. Also, many combinations could be possible with GF to create numerous MD-vdWhs with hybrid functionalities, potentially giving access to explore novel devices with unique hybrid properties. Herein, we demonstrate MD-vdWhs (2D+3D) of GF with molybdenum disulfide (MoS2) to investigate magnetotransport properties. Remarkably, MR of GF is increased from ∼130% to ∼210% at 5 K under an applied magnetic field of 5 T by fabricating its MD-vdWhs with MoS2. Our systematic investigations show that distinct magnetotransport properties in GF/MoS2 vdWhs are strongly correlated to the enhancement in spin-orbit-coupling of the MD-vdWhs. Together, these results present a promising path toward the fabrication of future sensing and memory devices.

Spin polarisation is investigated for electrons in a spin–orbit coupled, magnetically and electrically modulated semiconductor heterostructure, which can be fabricated by patterning a ferromagnetic...

Drumheadlike surface states are typical characteristics in nodal line semimetals and bring varieties of unusual attractive properties. Here we demonstrate the double drumheadlike surface states in group V elemental semimetals As, Sb, Bi, which family materials behave a nodal line topology with a 3D flowerlike nodal line, using first-principles calculations. On (001) surface of group V elemental semimetals, the projection pattern of the nodal line overlaps and a complicated double drumheadlike surface state appears inside the overlapped region. This double surface state is widely distributed on the surface region up to a penetration depth of 3.5 nm, which is much deeper than the depth of single surface state on (111) surface. Given that the simplicity of the elemental structure and the small gap induced by the spin orbit coupling, this family materials are promising candidates for the experimental observation of the novel double drumheadlike surface state.

Z 2 topology in two-dimensional group IVA materials has been explained by the band orders due to the crystal field splitting at the Γ point in the Brillouin zone, while spin-orbit coupling (SOC) was considered just to open a band gap. By using a multi-orbital tight-binding model, we show that the SOC induces band inversion between the conduction and valence bands at the Γ point in plumbene, which also is the case in stanene when the SOC strength increases. As a result of the band inversion, plumbene becomes a spin Chern insulator with a spin Chern number C S = 2 and, as the SOC strength increases, stanene undergoes a topological phase transition from a Z 2 topological insulator to a spin Chern insulator with C S = 2. Under a staggered AB-sublattice potential, plumbene undergoes a phase transition from the spin Chern insulator with C S = 2 to a Z 2 topological insulator with C S = 1.

Temperature dependence of anisotropic tensor susceptibility (ATS) scattering intensities of GdB4 were measured near L-edges of Gd to investigate how spin ordering affects ATS. ATS scattering intensities for L2- and L3-edges show different temperature dependence below TN. At L3-edge the intensities reflect spin order parameter while intensities at L2-edge do not show noticeable change. The difference is explained in terms of spin-orbit coupling and isotropic distribution of spin-polarized 5d states of Gd ions. Above TN ATS scattering intensities demonstrate that thermal motions enhance charge distribution anisotorpy of Gd 5d states in paramagnetic phase.

Carbon nanotubes (CNTs), helically wrapped with single-stranded DNA, have recently emerged as a spin-filtering material. The inversion asymmetric helical potential of DNA creates a spin-filtering effect (commonly known as "chirality-induced spin selectivity" or CISS), which polarizes carrier spins in the nanotube. Thus, tuning of the DNA-CNT interaction is expected to affect carrier spins in nanotubes. The CISS effect induces spin polarization, which is coupled with the carrier's momentum direction, and therefore, in one-dimensional systems, such as nanotubes, momentum flip must be accompanied by a simultaneous spin flip. This spin momentum locking can have a profound impact on charge transport in nanotubes as backscattering due to phonons and disorder will be suppressed as these mechanisms are spin-independent. Here, we report DNA-CNT spin filters in which CNTs have been functionalized with two different classes of sequences, exhibiting different degrees of interaction with the CNT. They induce different degrees of spin polarization in the channel, with significant impact on temperature-dependent charge transport and interference phenomena arising from carrier backscattering. This work raises the intriguing possibility of engineering charge transport in nanotubes

We theoretically investigate the crossed spin conductance (CSC) of a graphene-based heterostructure consists of ferromagnet, Rashba spin-orbit and superconductor regions. Using Dirac Bogoliubov-de Gennes formalism in the ballistic regime, we show that in the presence of Rashba spin-orbit coupling there are an anomalous crossed Andreev reection and spin-ipped co-tunneling in the process of quantum transport. We demonstrate that the CSC can be reversed with respect to charge conductance by tuning the Rashba spin-orbit coupling which experimentally can be adjusted by the applied perpendicular electric field on the graphene sheet. This feature in addition to a long spin relaxation time of Dirac fermions in graphene proposes designing a device with a non-local spin switch which is crucial for spintronics circuits.

Among the perovskite oxide family, KTaO3 (KTO) has recently attracted considerable interest as a possible system for the realization of the Rashba effect. In this work, we report a novel conducting interface by placing KTO with another insulator, LaVO3 (LVO) and report planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) measurements. This interface exhibits a signature of strong spin-orbit coupling. Our experimental observations of two fold AMR and PHE at low magnetic fields (B) is similar to those obtained for topological systems and can be intuitively understood using a phenomenological theory for a Rashba spin-split system. Our experimental data show a B2 dependence of AMR and PHE at low magnetic fields that could also be explained based on our model. At high fields (~8 T), we see a two fold to four fold transition in the AMR that could not be explained using only Rashba spin-split energy spectra. Two dimensional electron gas (2DEG) at oxide interfaces is promising in modern electronic devices. Here, Wadehra et al. realize 2DEG at a novel interface composed of LaVO3 and KTaO3, where strong spin-orbit coupling and relativistic nature of the electrons in the 2DEG, leading to anisotropic magnetoresistance and planar Hall effect.

Two-dimensional (2D) Dirac-like electron gases have attracted tremendous research interest ever since the discovery of free-standing graphene. The linear energy dispersion and nontrivial Berry phase play a pivotal role in the electronic, optical, mechanical, and chemical properties of 2D Dirac materials. The known 2D Dirac materials are gapless only within certain approximations, for example, in the absence of spin-orbit coupling (SOC). Here, we report a route to establishing robust Dirac cones in 2D materials with nonsymmorphic crystal lattice. The nonsymmorphic symmetry enforces Dirac-like band dispersions around certain high-symmetry momenta in the presence of SOC. Through μ-ARPES measurements, we observe Dirac-like band dispersions in α-bismuthene. The nonsymmorphic lattice symmetry is confirmed by μ-low-energy electron diffraction and scanning tunneling microscopy. Our first-principles simulations and theoretical topological analysis demonstrate the correspondence between nonsymmorphic symmetry and Dirac states. This mechanism can be straightforwardly generalized to other nonsymmorphic materials. The results enlighten the search of symmetry-enforced Dirac fermions in the vast uncharted world of nonsymmorphic 2D materials.

Directional coupling of light in nanophotonic circuits has recently attracted increasing interest, with numerous experimental realizations based on broken rotational or mirror symmetries of the light-matter system. The most prominent underlying effect is the spin-orbit interaction of light in subwavelength structures. Unfortunately, coupling of light to such structures is, in general, very inefficient. In this work, we experimentally demonstrate an order of magnitude enhancement of the directional coupling between two nanowaveguides by means of a whispering gallery microcavity. We also show that both transversmagnetic and transverse electric modes can be used for the enhancement., 3 figures

This paper focuses on the electronic and thermoelectric properties of monolayer MoS2. Here, we have examined the structure of MoS2, in which the hole in the center of the hexagonal cage is considered as a void atom, termed 1H-MoS2. Density functional theory (DFT) employing the generalized gradient approximation (GGA) and spin–orbit coupling (SOC) has been used for all calculations. Incorporation of SOC resulted in a significant change in the profile of the band energy, specifically the splitting of the valence band maximum (VBM) into two sub-bands. The “split-off” energy is found to be ∼20.6 meV. The reduction of the band gap with SOC is a prominent feature at the K–K location in the Brillouin zone. The band gap calculated with the GGA is ∼1.75 eV. However, on implementation of SOC, the GGA band gap was reduced to ∼1.68 eV. The frequency-dependent phonon dispersion curve was obtained to analyse the thermodynamical stability. 1H-MoS2 is found to be thermodynamically stable with no imaginary frequency. We report a low value of lattice thermal conductivity (κl) and low electron effective masses, which are desirable for potential applications in thermoelectric devices.

The exploration of topological states in materials is currently focused on metals and semimetals, and their linear band crossing features various topological states, including a nodal point, nodal line and nodal surface. Based on first principles calculations, we have predicted a ternary NdAsPd compound that exhibits multiple topological states of a type-II nodal ring, triply degenerate nodal point and nodal surface states in the absence of spin orbit coupling (SOC) effects. Its band formation mechanism has been analyzed and the corresponding nontrivial drumhead surface and Fermi arc have been confirmed. Under the consideration of SOC, these topological states evolve into a type-II nodal point and type-I nodal line. The remarkable topological diversity in the present material is very rare and can serve as a promising platform upon which to study the rich fermionic states in a single material.

In this paper, we investigate the electronic, optical, and thermoelectric properties of Ga2SSe monolayer by using density functional theory. Via analysis of the phonon spectrum and ab initio molecular dynamics simulations, Ga2SSe is confirmed to be stable at room temperature. Our calculations demonstrate that Ga2SSe exhibits indirect semiconductor characteristics and the spin–orbit coupling (SOC) effect has slightly reduced its band gap. Besides, the band gap of Ga2SSe depends tightly on the biaxial strain. When the SOC effect is included, small spin–orbit splitting energy of 90 meV has been found in the valence band. However, the spin–orbit splitting energy dramatically changes in the presence of biaxial strain. Ga2SSe exhibits high optical absorption intensity in the near-ultraviolet region, up to 8.444 × 104 cm−1, which is needed for applications in optoelectronic devices. By using the Boltzmann transport equations, the electronic transport coefficients of Ga2SSe are comprehensively investigated. Our calculations reveal that Ga2SSe exhibits a very low lattice thermal conductivity and high figure of merit ZT and we can enhance its ZT by temperature. Our findings provide further insight into the physical properties of Ga2SSe as well as point to prospects for its application in next-generation high-performance devices.