Simultaneous breaking of inversion- and time-reversal symmetry in Josephson junction (JJ) leads to a possible violation of theI(φ) = −I(−φ) equality for the current–phase relation. This is known as anomalous Josephson effect and it produces a phase shiftφ₀in sinusoidal current–phase relations. In ballistic JJs with non-sinusoidal current phase relation the observed phenomenology is much richer, including the supercurrent diode effect and the magnetochiral anisotropy (MCA) of Josephson inductance. In this work, we present measurements of both effects on arrays of JJs defined on epitaxial Al/InAs heterostructures. We show that the orientation of the current with respect to the lattice affects the MCA, possibly as the result of a finite Dresselhaus component. In addition, we show that the two-fold symmetry of the Josephson inductance reflects in the activation energy for phase slips.

Nanowires induce mechanical deformations in monolayer semiconductors, creating potential channels that guide optical excitations.

Semiconductor nanowires based on non-nitride III-V compounds can be synthesized under certain growth conditions to favor the appearance of the wurtzite crystal phase. Despite reports in the literature of ab initio band structures for these wurtzite compounds, we still lack effective multiband models and parameter sets that can be simply used to investigate physical properties of such systems, for instance, under quantum confinement effects. In order to address this deficiency, in this study we calculate the ab initio band structure of bulk InAs and InP in the wurtzite phase and develop an $8\times 8$ $k·p$ Hamiltonian to describe the energy bands around the $\mathrm{\Gamma }$ point. We show that our $k·p$ model is robust and can be fitted to describe the important features of the ab initio band structure. The correct description of the spin-splitting effects that arise due to the lack of inversion symmetry in wurtzite crystals is obtained with the $k$-dependent spin-orbit term in the Hamiltonian, often neglected in the literature. All the energy bands display a Rashba-like spin texture for the in-plane spin expectation value. We also provide the density of states and the carrier density as functions of the Fermi energy. Alternatively, we show an analytical description of the conduction band, valid close to the $\mathrm{\Gamma }$ point. The same fitting procedure is applied to the $6\times 6$ valence band Hamiltonian. However, we find that the most reliable approach is the $8\times 8$ $k·p$ Hamiltonian for both compounds. The $k·p$ Hamiltonians and parameter sets that we develop in this paper provide a reliable theoretical framework that can be easily applied to investigate electronic, transport, optical, and spin properties of InAs- and InP-based nanostructures.

Phosphorene, a single layer of black phosphorus, is a direct band gap two-dimensional semiconductor with promising charge and spin transport properties. The electronic band structure of phosphorene is strongly affected by the structural anisotropy of the underlying crystal lattice. We describe the relevant conduction and valence bands close to the $\mathrm{\Gamma }$-point by four- and six-band (with spin) $k·p$ models, including the previously overlooked interband spin-orbit coupling which is essential for studying anisotropic crystals. All the $k·p$ parameters are obtained by a robust fit to ab initio data, by taking into account the nominal band structure and the $k$-dependence of the effective mass close to the $\mathrm{\Gamma }$-point. The inclusion of interband spin-orbit coupling allows us to determine dipole transitions along both armchair and zigzag directions. The interband coupling is also key to determine the effective $g$-factors and Zeeman splittings of the Landau levels. We predict the electron and hole $g$-factor correction of $\approx 0.03$ due to the intrinsic contributions in phosphorene, which lies within the existing range of experimental data. Furthermore, we investigate excitonic effects using the $k·p$ models and find exciton binding energy (0.81 eV) and exciton diameters consistent with experiments and ab initio based calculations. The proposed $k·p$ Hamiltonians should be useful for investigating magnetic, spin, transport, and optical properties and many-body effects in phosphorene.

Transition metal dichalcogenides (TMDCs) are ideal candidates to explore the manifestation of spin-valley physics under external stimuli. In this study, we investigate the influence of strain on the spin and orbital angular momenta, effective g-factors, and Berry curvatures of several monolayer TMDCs (Mo and W based) using a full ab initio approach. At the K-valleys, we find a surprising decrease of the conduction band spin expectation value for compressive strain, consequently increasing the dipole strength of the dark exciton by more than one order of magnitude (for ∼ 1 % – 2 % strain variation). We also predict the behavior of direct excitons g-factors under strain: tensile (compressive) strain increases (decreases) the absolute value of g-factors. Strain variations of ∼1% modify the bright (A and B) excitons g-factors by ∼0.3 (0.2) for W (Mo) based compounds and the dark exciton g-factors by ∼0.5 (0.3) for W (Mo) compounds. Our predictions could be directly visualized in magneto-optical experiments in strained samples at low temperature. Additionally, our calculations strongly suggest that strain effects are one of the possible causes of g-factor fluctuations observed experimentally. By comparing the different TMDC compounds, we reveal the role of spin–orbit coupling (SOC): the stronger the SOC, the more sensitive are the spin-valley features under applied strain. Consequently, monolayer WSe₂ is a formidable candidate to explore the role of strain on the spin-valley physics. We complete our analysis by considering the side valleys, Γ and Q points, and by investigating the influence of strain in the Berry curvature. In the broader context of valley- and strain-tronics, our study provides fundamental microscopic insights into the role of strain in the spin-valley physics of TMDCs, which are relevant to interpret experimental data in monolayer TMDCs as well as TMDC-based van der Waals heterostructures.

An effective model of the hexagonal (NiAs-structure) manganese telluride valence band in the vicinity of the $A$ point of the Brillouin zone is derived. It is shown that whereas for the usual antiferromagnetic order (magnetic moments on the basal plane) band splitting at $A$ is small, their out-of-plane rotation enhances the splitting dramatically (to about 0.5 eV). We propose extensions of recent experiments [ Phys. Rev. Mater. 6, 014404 (2022)] where such inversion of magnetocrystalline anisotropy has been observed in Li-doped MnTe to confirm this unusual sensitivity of a semiconductor band structure to magnetic order.