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Unstrained Ge1-xSnx layers of various Sn concentration (1.5%, 3%, 6% Sn) and Ge0.97Sn0.03 layers with built-in compressive (ε=-0.5%) and tensile (ε=0.3%) strain are grown by molecular beam epitaxy and studied by electromodulation spectroscopy (i.e., contactless electroreflectance and photo-reflectance (PR)). In order to obtain unstrained GeSn layers and layers with different built-in in-plane strains, virtual InGaAs substrates of different compositions are grown prior to the deposition of GeSn layers. For unstrained Ge1-xSnx layers, the pressure coefficient for the direct band gap transition is determined from PR measurements at various hydrostatic pressures to be 12.2±0.2meV/kbar, which is very close to the pressure coefficient for the direct band gap transition in Ge (12.9 meV/kbar). This suggests that the hydrostatic deformation potentials typical of Ge can be applied to describe the pressure-induced changes in the electronic band structure of Ge1-xSnx alloys with low Sn concentrations. The same conclusion is derived for the uniaxial deformation potential, which describes the splitting between heavy-hole (HH) and light-hole (LH) bands as well as the strain-related shift of the spin-orbit (SO) split-off band. It is observed that the HH, LH, and SO related transitions shift due to compressive and tensile strain according to the Bir-Pikus theory. The dispersions of HH, LH, and SO bands are calculated for compressive and tensile strained Ge0.97Sn0.03 with the 8-band kp Hamiltonian including strain effects, and the mixing of HH and LH bands is discussed. In addition, the dispersion of the electronic band structure is calculated for unstrained Ge1-xSnx layers (3% and 6% Sn) at high hydrostatic pressure with the 8-band kp Hamiltonian, and the pressure-induced changes in the electronic band structure are discussed. [ABSTRACT FROM AUTHOR]

The three-nucleon force (3NF) is crucial in shaping the shell structure of atomic nuclei, particularly impacting the enhancement of spin-orbit (SO) splitting, especially in nuclei with significant deviations from stability. Despite its importance, the specific mechanisms driving this enhancement remain unclear. In this study, we introduce a decomposition scheme based on the rank of irreducible tensors forming the 3NF, derived from chiral effective field theory at next-to-next-to-leading order, to elucidate their influence on SO splitting. Within the shell-model framework, our analysis reveals that the rank-1 component of the 3NF is the primary factor enlarging the energy gap between the 0 p 3 / 2 and 0 p 1 / 2 single-particle levels in p -shell nuclei, while the rank-2 component makes a subdominant contribution. Since the rank-1 component originates exclusively from the 2 π -exchange 3NF, our finding will not depend on the choice of the low-energy constants of contact terms. We also remark on the antisymmetry of the rank-1 3NF, which can affect the quantum entanglement of spin states. This study lays the groundwork for further exploration into this field toward a microscopic understanding of the 3NF impact on the nuclear shell structure. [ABSTRACT FROM AUTHOR]

We report the results of first-principles calculations based on the full-potential linearized augmented plane wave (FP-LAPW + lo) method to explore the effects of alloying under the non-conventional AlN III-V compound with bismuth. We have calculated the structural and electronic properties of the binary compounds AlN and AlBi in the zinc blend structure. We have found a good agreement between our results and the experimental and theoretical results available for that binary compounds which may be a support for the results of the ternary alloys. For the AlNBi ternary alloys, we have found a rapid reduction of the energy gap by 1.31 eV/%Bi accompanied by a strong increase in the spin-orbit splitting energy (Δ) with increasing Bi composition. We have also shown that the Δ becomes greater than the energy gap for composition of Bi about 4.2% (Δ > E ). This result is significant due to the possibility of suppressing Auger recombination, which is expected to improve the high temperature performance and thermal stability of light emitting devices. Finally, we have calculated the variation of the optical properties of AlNBi compounds, such as dielectric function and refractive index versus Bi composition. [ABSTRACT FROM AUTHOR]

We have developed a 10- and 14-band anticrossing (BAC) models to investigate the band structures of dilute nitrides and dilute bismides alloys. In fact, the addition of Bi or N to III-V semiconductors causes a significant reduction in the band gap energy and an enhancement of the spin-orbit splitting energy. Further, the conduction and valence offsets between III-V-N/III-V-Bi were also investigated for different nitrogen and bismuth concentrations. For III-V-N/III-V-Bi heterojunctions, the strain-balanced criteria were undertaken by the zero stress analysis. The band alignment of strain-balanced GaAsN/GaAsBi, InPN/InPBi and InAsN/InAsBi is a type II. For InSbN/InSbBi heterostructure, the band lineup can be type I or II. [ABSTRACT FROM AUTHOR]

We study Hall and Nernst transports in monolayer MoS2 based on Green's function formalism. We have derived analytical results for spin and valley Hall conductivities in the zero temperature and spin and valley Nernst conductivities in the low temperature. We found that tuning of the band gap and spin-orbit splitting can drive system transition from spin Hall insulator (SHI) to valley Hall insulator (VHI). When the system is subjected to a temperature gradient, the spin and valley Nernst conductivities are dependent on Berry curvature. [ABSTRACT FROM AUTHOR]

We study Hall and Nernst transports in monolayer MoS2 based on Green's function formalism. We have derived analytical results for spin and valley Hall conductivities in the zero temperature and spin and valley Nernst conductivities in the low temperature. We found that tuning of the band gap and spin-orbit splitting can drive system transition from spin Hall insulator (SHI) to valley Hall insulator (VHI). When the system is subjected to a temperature gradient, the spin and valley Nernst conductivities are dependent on Berry curvature. [ABSTRACT FROM AUTHOR]

We propose a nonoptical mechanism for generating spin current via Auger recombination in semiconductor quantum wells (QWs) with spin-orbit splitting associated with structural QW asymmetry. It is shown that Auger recombination in narrow-bandgap semiconductors makes it possible to produce spin currents that exceed those that are obtained in the case of intraband as well as interband optical excitation. Analysis shows that the interference term in the expression for the Auger-recombination rate is responsible for the generation of spin currents. [ABSTRACT FROM AUTHOR]

As the most important material parameter of semiconductor, bandgap is necessary to be investigated to meet the design requirements of the high-performance optoelectronic devices. A new method of is proposed to calibrate the bandgap of antimonide based multi-component alloys with considering the effect of spin-orbit splitting off bands and the doublet degeneracy of valance band on the bandgaps of Sb-containing materials. A correction factor is introduced in the conventional calculation, and the spin-orbit splitting method is proposed. Besides, the InxGa1-xAsySb1-y films with different compositions are grown on GaSb substrates by molecular beam epitaxy, and the corresponding bandgaps are obtained by photoluminescence to test the accuracy and reliability of this new method. An error rate analysis reveals that the α calculated by the spin-orbit splitting correction method is decreased to 2%, almost one order of magnitude smaller than the Moon method, which means that the new method can calculate the antimonide multicomponent more accurately with some applicability. This work can give a reasonable interpretation for the reported results and beneficial to tailor the antimonides properties and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Contactless electroreflectance is applied to study the band gap (E0) and spin-orbit splitting (ΔSO) in InP1-xBix alloys with 0 < x ≤ 0.034. The E0 transition shifts to longer wavelengths very significantly (-83meV/% Bi), while the E0 + ΔSO transition shifts very weakly (-13meV/% Bi) with the rise of Bi concentration. These changes in energies of optical transitions are discussed in the context of the valence band anticrossing model and ab initio calculations. Shifts of E0 and E0 + ΔSO transitions, obtained within ab-initio calculations, are -106 and -20meV per % Bi, respectively, which is in a good agreement with experimental results. [ABSTRACT FROM AUTHOR]

In a cubic topological insulator (TI), there is a band inversion whereby the s-like Γ6c conduction band is below the p-like Γ7v+Γ8v valence bands by the "inversion energy" Δi<0. In TIs based on the zinc-blende structure such as HgTe, the Fermi energy intersects the degenerate Γ8v state so the insulating gap Eg between occupied and unoccupied bands vanishes. To achieve an insulating gap Eg>0 critical for TI applications, one often needs to resort to structural manipulations such as structural symmetry lowering (e.g., Bi2Se3), strain, or quantum confinement. However, these methods have thus far opened an insulating gap of only <0.1 eV. Here we point out that there is an electronic rather than structural way to affect an insulating gap in a TI: if one can invert the spin-orbit levels and place Γ8v below Γ7v ("nEgative spin-orbit splitting"), one can realize band inversion (Δi<0) with a large insulating gap (Eg up to 0.5 eV). We outline design principles to create nEgative spin-orbit splitting: hybridization of d orbitals into p-like states. This general principle is illustrated in the "filled tetrahedral structures" (FTS) demonstrating via GW and density functional theory (DFT) calculations Eg>0 with Δi<0, albeit in a metastable form of FTS. [ABSTRACT FROM AUTHOR]