Spin-orbit Coupling Research Articles

Cumulated Effects of Magnetic Field, Electron–Phonon and Spin–Orbit Interaction on Thermodynamics Properties of Mono Layer Graphene

Cumulated Effects of Magnetic Field, Electron–Phonon and Spin–Orbit Interaction on Thermodynamics Properties of Mono Layer Graphene

Dynamic Jahn-Teller effect in the strong spin-orbit coupling regime

Exotic quantum phases, arising from a complex interplay of charge, spin, lattice and orbital degrees of freedom, are of immense interest to a wide research community. A well-known example of such an entangled behavior is the Jahn-Teller effect, where the lifting of orbital degeneracy proceeds through lattice distortions. Here we demonstrate that a highly-symmetrical 5d1 double perovskite Ba2MgReO6, comprising a 3D array of isolated ReO6 octahedra, represents a rare example of a dynamic Jahn-Teller system in the strong spin-orbit coupling regime. Thermodynamic and resonant inelastic x-ray scattering experiments, supported by quantum chemistry calculations, undoubtedly show that the Jahn-Teller instability leads to a ground-state doublet, resolving a long-standing puzzle in this family of compounds. The dynamic state of ReO6 octahedra persists down to the lowest temperatures, where a multipolar order sets in, allowing for investigations of the interplay between a dynamic JT effect and strongly correlated electron behavior.

Electrochemical analysis of sol-gel and hydrothermal synthesized mesoporous strontium titanate spherical nanoparticles as electrode material for high-performance flexible supercapacitors

Perovskite oxides with large specific surface areas present a promising avenue for enhancing supercapacitor efficiency. This study investigates the remarkable charge storage capabilities of strontium titanate (SrTiO3, STO) synthesized via sol-gel and hydrothermal techniques for electrochemical energy storage applications. The cubic crystal structure of STO, confirmed from X-ray Diffraction analysis, synthesized at lower temperatures through both methods, provides three-dimensional diffusion channels for oxygen anion movement, which is crucial for improving charge storage capacity. X-ray photoelectron spectroscopy confirmed the elements’ oxidation states and their spin-orbit splitting. The spherical nanoparticle morphology was observed in the FESEM images, BET characterization revealed a high specific surface area contributing to more charge storage and mesoporous nature facilitates excellent mass transfer rates of electrolytic ions. Electrochemical measurements and calculations confirmed that sol-gel and hydrothermally synthesized STO electrodes exhibit maximum specific capacitances of 130 F g−1 and 156 F g−1 at 10 mV s−1, respectively. A fabricated flexible supercapacitor device in an aqueous medium maintains a constant voltage of 1.2 V, capable of powering a digital watch. Hence, this study demonstrates the potential of STO electrode-based supercapacitors for a wide range of electrochemical energy storage applications.

Superconducting diode effect in diffusive superconductors and Josephson junctions with Rashba spin-orbit coupling

Superconducting diode effect in diffusive superconductors and Josephson junctions with Rashba spin-orbit coupling

Unraveling the Spin-to-Charge Current Conversion Mechanism and Charge Transfer Dynamics at the Interface of Graphene/WS2 Heterostructures at Room Temperature.

We report experimental investigations of spin-to-charge current conversion and charge transfer (CT) dynamics at the interface of the graphene/WS2 van der Waals heterostructure. Pure spin current was produced by the spin precession in the microwave-driven ferromagnetic resonance of a permalloy film (Py=Ni81Fe19) and injected into the graphene/WS2 heterostructure through a spin pumping process. The observed spin-to-charge current conversion in the heterostructure is attributed to the inverse Rashba-Edelstein effect (IREE) at the graphene/WS2 interface. Interfacial CT dynamics in this heterostructure was investigated based on the framework of the core-hole clock (CHC) approach. The results obtained from spin pumping and CHC studies show that the spin-to-charge current conversion and charge transfer processes are more efficient in the graphene/WS2 heterostructure compared to isolated WS2 and graphene films. The results show that the presence of WS2 flakes improves the current conversion efficiency. These experimental results are corroborated by density functional theory (DFT) calculations, which reveal (i) Rashba spin-orbit splitting of graphene orbitals and (ii) electronic coupling between graphene and WS2 orbitals. This study provides valuable insights for optimizing the design and performance of spintronic devices.

Engineered Josephson diode effect in kinked Rashba nanochannels

The superconducting diode effect, reminiscent of the unidirectional charge transport in semiconductor diodes, is characterized by a nonreciprocal, dissipationless flow of Cooper pairs. This remarkable phenomenon arises from the interplay between symmetry constraints and the inherent quantum behavior of superconductors. Here, we explore the geometric control of the diode effect in a kinked nanostrip Josephson junction based on a two-dimensional electron gas (2DEGs) with Rashba spin-orbit interaction. We provide a comprehensive analysis of the diode effect as a function of the kink angle and the out-of-plane magnetic field. Our analysis reveals a rich phase diagram, showcasing a geometry and field-controlled diode effect. The phase diagram also reveals the presence of an anomalous Josephson effect related to the emergence of trivial zero-energy Andreev bound states, which can evolve into Majorana bound states. Our findings indicate that the exceptional synergy between geometric control of the diode effect and topological phases can be effectively leveraged to design and optimize superconducting devices with tailored transport properties.

Topological phase engineering of rutile GeO2 with strain

Nodal-line semimetals serve as the parent phase for various topological states. By manipulating spin-orbit coupling (SOC), time-reversal symmetry, or spatial inversion symmetry, a Dirac nodal-line semimetal can transition into a 3D Dirac semimetal, Weyl semimetal, or topological insulator.In this study, we present the topological phase engineering of rutile GeO2 under strain through first-principles calculations. Without considering SOC effect, applying tensile strain to GeO2 induces a transformation from a trivial insulator to a Dirac nodal-line semimetal, characterized by two orthogonal and interconnected Dirac nodal rings protected by mirror symmetry. When SOC is taken into account, the band degeneracy persists only at two points, resulting in a 3D Dirac semimetal. Nonetheless, due to the negligible strength of SOC in GeO2, its nodal-line semimetal properties remain largely intact even after including SOC effects.Our findings provide valuable insights for the topological phase engineering and potential spintronics applications of GeO2.

Exploring the inorganic perovskite materials Mg3SbX3 (Where, X=I, Br, Cl and F) through the perspective of density function theory: Adjustment of physical characteristics as consequence of strain

The solar technology industry has lately given inorganic perovskite materials an abundance of thought because of their unique optical, electrical and structural characteristics. Issues pertaining to lead (Pb) toxicity and instability require being referred to promptly, making lead-free atomically designed metal halide perovskites of foremost importance to the photovoltaic and optoelectronic industries. Perovskites, a class of inorganic metal halide semiconductors, have variant similarities with (X=I, Br, Cl and F). According to the space group Pm-3m (X=I, Br, Cl and F) has a cubic perovskite crystal structure. Utilizing first-principles density-functional theory (FPDFT), The intention of this investigation is to analyze how strain and spin-orbit coupling (SOC) impact the structural, electrical, optical and mechanical features of the inorganic cubic perovskite of (X=I, Br, Cl and F). At the point between R and Γ, the molecule displays an indirect bandgap of 0.105 eV, 0.957 eV, 1.728 eV. At the Γ point, the molecule displays a direct bandgap of 3.184 eV. The bandgaps of the and perovskites are 0.198 eV, 1.203 eV, 1.901 eV and 3.723 eV respectively, when considering the spin-orbital coupling (SOC) quantum influence. A wider bandgap is investigated for increasing compressive strain while a smaller bandgap is observed for increasing tensile strain. Apart from the elastic constants and anisotropic factors, other factors that are anticipated include Pugh's ratio, Poisson's ratio, bulk modulus and others. Isotropic, ductile and mechanically stable are the words that best describe these materials, according to the elastic property evaluations. In the photon energy range that is appropriate for solar cells, the dielectric constant spikes of are found to be visible. Therefore, (X=I, Br, Cl and F) perovskite is a good material to use in solar cells for managing light and producing electricity.

Harnessing orbital Hall effect for efficient orbital torque in light metal vanadium

The orbital Hall effect depicts the conversion of charge current to orbital current in nonmagnetic materials without spin–orbit coupling. This absence of spin–orbit coupling enables the light metals serve as sources of orbital current exploited as the information carrier to be applied to the information technology. Here, we investigate current-induced torques in vanadium/ferromagnet (V/FM, FM = Fe, Co, Ni81Fe19) bilayers via spin-torque ferromagnetic resonance (ST-FMR) system. The sign reversal confirms that the orbital Hall effect exists in light metal V, and the orbital torque in V/Co and V/Ni81Fe19 bilayers is dominant. By performing the V thickness dependence of conversion efficiency, we determined the orbital diffusion length of 3.61 nm for V. Our experiment demonstrates that light metals can be used as novel materials in spin–orbit devices, and our research focuses on the orbital freedom of the electron and provides new content for the study of orbital dynamics.

The electronic and optical properties of group III-V semiconductors: Arsenides and antimonides

Investigating the structural, electronic, and optical properties of zinc-blende III-V semiconductors, particularly arsenides, and antimonides, which are crucial for optoelectronic devices such as transistors, infrared detectors, and quantum technologies due to their wide range of direct bandgaps. In this work, we have employed a first-principles approach integrating G0W0 with the HSE06 hybrid functional and spin–orbit coupling (SOC) to study their fundamental properties. Traditional Density Functional Theory (DFT) methods, particularly those using Generalized Gradient Approximation (GGA) PBE functionals, tend to underestimate bandgaps, leading to discrepancies with experimental results. To address this, our study corrects the bandgap underestimation and refines the calculation of optical constants, including the dielectric function, refractive index, extinction coefficient, and absorption coefficient. Moreover, the optimized lattice constants and electronic properties derived from our computational model strongly correlate with experimental data, demonstrating the model’s reliability in predicting material properties. The findings suggest that our methods can be applied to arsenides and antimonides, offering a pathway to designing materials with optoelectronic properties involving III-V compounds and their complex heterostructures for advanced device applications.

First-principles calculations to investigate Electronic, Optical, Mechanical, and transport characteristics of novel A2BAuCl6 (A = K/Rb/Cs; B = Sc/Y)

By utilizing FP-LAPW, the structure, electronic, optical, mechanical and Transport characteristic of A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) were examined by using DFT. The analysis to the band structure plot of the Halide double perovskites (HDP’s) being studied indicated the existence of indirect band-gaps. The compounds A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) exhibit anisotropic properties, except one compound as seen by their respective shear anisotropy readings of 0.629, 0.532, 1.006, 0.682, 0.803 and 0.977. The materials have inherent ductility, as indicated by their calculated Poisson’s ratios in the range of 0.30 to 0.35. The examined (HDP’s) materials appear to possess indirect band-gaps, as indicated by the band structure plots. The functional inorganic perovskites A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) haven’t similar band-gap values, as determined using the TB-mBJ (modified Becke Johnson) and TB-mBJ + Soc (Spin orbital coupling) assumptions. The visible and ultraviolet domain have prominent peaks, suggesting potential applications of the compounds in solar cells. Moreover, examination of additional optical characteristics such as reflectivity, conductivity, electron energy loss, and absorption coefficients suggest that it possesses the inherent features of a semiconductor. The maximum figure of merit for all the student compounds is above 0.74. The simulated output forms the foundation for A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) and are of practical importance for multijunction solar cells.

A comprehensive DFT Study of the electronic structure and optical properties of Iodine-based halide double perovskites for photovoltaic applications

This study aims to explore the electronic structure, thermodynamic, mechanical stability, and optical response of Iodine-based ordered vacancy double halide perovskite compounds through the application of density functional theory. The two compounds Cs2ZrI6 and Rb2ZrI6 exhibit thermodynamic stability, with displaying particularly notable. Moreover, analysis of the calculated coefficients of elastic stiffness confirms the mechanical stability of all materials under ambient pressure conditions. By using the Density Functional Theory with Spin-Orbit Coupling (SOC), it was observed that Cs2TeI6 and Rb2TeI6 possess an indirect band gap located between the X and L high-symmetry points, this show that Cs2TeI6, Rb2ZrI6, Cs2HfI6, and Rb2HfI6 are identified as direct semiconductor compounds. Moreover, the band gap values of X2YI6 (where X = Cs, Rb, and Y = Te, Zr, and Hf) exhibit an increasing trend as we progress along the alkali and transition metal elements in the periodic table, ranging from 1.422 eV for Cs2TeI6 to 2.465 eV for Rb2TeI6. Besides, the optical behavior of the visible light show that X2YI6 compounds have a high absorption of about 70%, reflectance of 30%, and a low transmittance. Thanks to their advantageous bandgap, enduring stabilities, and effective absorption of visible light, Cs2TeI6 and Rb2TeI6 hold significant promise for a wide range of electronic and optoelectronic applications, particularly in photovoltaics.

Structural, magnetic, elastic, and thermoelectric properties of Ba2InOsO6 double perovskite in the cubic phase: A DFT + U study with spin-orbit-coupling

In this study, we comprehensively investigate the structural, electronic, magnetic, elastic, and thermal properties of the double perovskite Ba2InOsO6 using density functional theory (DFT). Our results show that the ferromagnetic phase is the most stable, with the net magnetic moment primarily arising from the Os atom. The half-metallic behavior exhibited by Ba2InOsO6, characterized by a band gap of 3.62 eV in the TB-mBJ + U approximation, decreases upon the inclusion of spin–orbit coupling (SOC). This half-metallic property, coupled with the stability of the ferromagnetic phase, makes Ba2InOsO6 particularly suitable for spintronic applications, as it can facilitate efficient spin injection and transport. Elasticity analysis indicates moderate brittleness, while thermoelectric properties, calculated using the Boltzmann transport model, reveal n-type conductivity and notable thermopower, suggesting potential for thermoelectric applications. This work provides a solid foundation for future experimental studies and potential applications in advanced technologies.

Crystal structures and electronic and magnetic properties of Janus bilayer Cl[formula omitted]Cr[formula omitted]I[formula omitted]

Two-dimensional (2D) magnetic material CrI3 has aroused extensive attention, because it could provide a new platform for investigating the relations between crystal structures and electronic and magnetic properties. Here, we study crystal structures and electronic and magnetic properties of three configurations (Cl-Cl I-I and Cl-I) of Janus bilayer Cl3Cr2I3 with two stacking orders (AB and AA1/3) by using the first principles approach incorporating the spin–orbit coupling (SOC) effect and the dipole correction. It is found that the spin polarization and the SOC effect can expand the lattice constant and the interlayer distance (ID) of the three configurations. Especially, the ID of the I-I configuration is 1 Å larger than that of the Cl-Cl configuration. The total energy calculation results show that the atomic configuration, the SOC effect and the stacking order play an important role in determining the magnetic ground states of the Janus layers. Our results indicate the atomic configurations of the Janus bilayers are not conducive to the increase of critical temperature. Interestingly, the Cl-I configuration has a vertical dipole moment, and its AFM state has large spin splitting. It is revealed that the non-periodic structure, the symmetry breaking of the average potential and the weak interlayer interaction lead to the vertical dipole moment and the abnormal AFM state that is not the most stable state.

Thionation of conjugated porphyrin with enhanced photodynamic and photothermal effects for cancer therapy

Phototherapy has emerged as a promising modality for cancer treatment in recent years, owing to its precise temporal control and minimally invasive nature. Here, two new organic porphyrin molecules, denoted as ONP and SNP, were designed and synthesized with an acceptor–donor–acceptor (A-D-A) architecture. The donor–acceptor (D-A) pairs in molecules facilitated the intermolecular charge transfer (ICT), thereby amplifying near-infrared (NIR) absorbance and promoting nonradiative heat generation. Notably, the substitution of oxygen atoms with sulfur in naphthalimides (NI) led to significant change of their photophysical and photochemical properties. Specifically, the sulfur atoms exhibited pronounced spin–orbit coupling (SOC) effect, leading to efficient photoinduced intersystem crossing (ISC) processes, thus facilitating the generation of reactive oxygen species (ROS). Upon self-assembly, the formed nanomaterials (ONP NPs and SNP NPs) exhibited spherical morphology with average size about 150 nm. The biocompatibility and photocytotoxicity of nanoparticles against Hepa1-6 cells were evaluated using the CCK-8 assay. Additionally, the synergistic effects (photodynamic therapy and photothermal therapy) of SNP NPs were confirmed through diverse in vitro experiment under 690 nm laser irradiation. The generation of intracellular ROS by SNP NPs was confirmed with DCFH-DA as probe. This study provides an ingenious strategy for developing organic nanomaterials with high treatment efficiency through synergistic photodynamic/photothermal effects.

Theoretical study on the spectrum properties of tellurium iodide cation

The molecular potential energy function plays an important role in many fields. In this paper, the icMRCI + Q method was utilized to compute the potential energy and dipole moments for 22 Λ-S states and 51 Ω states of the TeI+ system. Two basis sets (AVQZ-PP and AWCVQZ-PP) were employed to compute the TeI+ system, with the results indicating that the AVQZ-PP basis set yielded more accurate results. Therefore, all calculations in this paper are based on this basis set. Furthermore, to ensure the accuracy of the results, a comparison was conducted on the spectral parameters of the ground state and two excited states of the molecular ion within the same main group. Given the significant impact of spin–orbit coupling, as indicated by the calculated SO matrix elements, our discussion will predominantly center on the avoidance of crossovers in the Ω states. Finally, the Franck-Condon factors, Einstein coefficients and radiative lifetime between these two states were calculated from the data of the transition between the X3Σ0+-↔11Σ0++ of the TeI+ molecule.

Electrochemical synthesis of multicolor carbon dots with room temperature phosphorescence to thermally activated delayed fluorescence via surface state modulation

Solid-state multicolor carbon dots (CDs) have attracted tremendous attention due to their wide applications. However, the fluorescence quenching of solid-state CDs occurs due to the π-π stacking or energy transfer between adjacent carbon dots. In addition, it is difficult to observe the afterglow of solid-state CDs due to their self-quenching and deliquescence. Here, electrochemically prepared multicolor CDs emit the solid-state fluorescence and afterglow emission with lifetimes up to 657 ms by embedding the CDs into urea matrix. More importantly, the surface amino groups and C = O bonds regulate the afterglow emission of CDs from phosphorescence and thermally activated delayed fluorescence at room temperature. Surface amino groups of multicolor CDs can enhance the spin–orbit coupling, increase the intersystem crossing (ISC) and reverse intersystem crossing (RISC). Thus it can promote the generation of triple excited states and regulate the singlet–triplet energy gap value from 0.384 to 0.026 eV. The formation of covalent bonds stabilizes the single and triple excited states and inhibits the non-radiative recombination, which achieves the enhanced fluorescence and visual afterglow of multicolor CDs. The fluorescence and afterglow CDs can be applied to dual signal imaging and anti-counterfeiting, which broadens the practical applications for solid-state CDs via surface state modulation.

ESIPT-induced intersystem crossing leads to tautomer fluorescence quenching for 3-mercapto-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one molecule

The excited-state intramolecular proton-transfer (ESIPT) dynamics of 2-(4-(diethylamino)phenyl)-3-mercapto-4H-chromen-4-one (3NTF) and 3-mercapto-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one (3FTF) have been investigated using time-dependent density functional theory (TDDFT). Upon photoexcitation, 3NTF exhibits a single fluorescence emission while 3FTF is fluorescence quenched when dissolved in cyclohexane solution. The present study reveals that both species undergo barrierless ESIPT process, and the underlying reason for fluorescence quenching in 3FTF has been elucidated. Specifically, it is concluded that intersystem crossing (ISC) is responsible for the fluorescence quenching in the 3FTF molecule due to the energy gap between the S1 and T2 states is only 0.12 eV plus large S1 → T2 spin–orbit coupling resulting in a strong interaction between the singlet and triplet states. The present study provides a reference for the fluorescence quenching associated with thiol-hydrogen bond molecules, and it is helpful for further research on ESIPT reactions of sulfur-containing molecules.

Studying the optical and electronic properties of Eu-doped CdSe phosphors using first principles calculations incorporating the spin orbit coupling method of DFT

We studied the electronic and optical properties of pure and Eu-doped CdSe phosphor materials using the first-principles calculation method, which is a feature of Density Functional Theory. The FP-LAPW method was employed for the study as incorporated in the Wien2k code. The GGA + U + SOC method of DFT was used for the first time in our study to investigate the electronic as well as optical characteristics of Eu-doped CdSe materials. Eu doping was done in two different ratios to study the effects of altered dopant concentration. The doping increased the band gap of the pure CdSe parental material. The calculated band gaps in our study were 0.42 eV for pure CdSe, 0.67 eV for a single Eu atom doped in CdSe, and 1.64 eV for two Eu atoms doped in CdSe. The measured electronic and optical characteristics of undoped i.e, pure CdSe and Eu-doped CdSe showed that the doping significantly changed the optical behavior of CdSe, which may be useful for applications in phosphor-converted LEDs.

Beyond the random phase approximation (RPA): first principles calculation of the valence EELS spectrum for KBr including local field, quasiparticle, excitonic and spin orbit coupling effects.

Beyond the random phase approximation (RPA): first principles calculation of the valence EELS spectrum for KBr including local field, quasiparticle, excitonic and spin orbit coupling effects.