Quasiparticles with Dirac-type dispersion can be observed in nearly gapless bulk semiconductors alloys in which the bandgap is controlled through the material composition. We demonstrate that the Dirac dispersion can be realized in short-period InAsSb/InAsSb metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain. The new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity v, and the dispersion corresponding to the motion in the growth direction is quadratic. Experimental estimate of the Fermi velocity gives v = 6.7 × 10 m/s. Remarkably, the Fermi velocity in this system can be controlled by varying the overlap between electron and hole states in the superlattice. Extreme design flexibility makes the short-period metamorphic InAsSb/InAsSb superlattice a new prospective platform for studying the effects of charge-carrier chirality and topologically nontrivial states in structures with the inverted bandgaps.

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Metamorphic strain compensated InSb/InAsSb0.52 superlattices (SLs) with ultrathin layers and different periods grown on GaSb substrate were designed, fabricated, and characterized. It was shown that a period increase from 3 to 6.2 nm reduced the effective bandgap energy from 70 to 0 meV. A further increase in the period leads to inversion of the valence and conduction bands. Magneto-optical experiments demonstrated that Dirac-like carrier dispersion is characteristic of almost gapless InSb/InAsSb0.52 SLs. Indication of hole transport enhancement over that found in InAsSb/InAsSb SL structures is presented.

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A Dirac-type energy spectrum was demonstrated in gapless ultra-short-period metamorphic InAsSb/InSb superlattices by angle-resolved photoemission spectroscopy (ARPES) measurements. The Fermi velocity value 7.4x10 5 m/s in a gapless superlattice with a period of 6.2nm is in a good agreement with the results of magneto-absorption experiments. An "inverted" bandgap opens in the center of the Brillouin zone at higher temperatures and in the SL with a larger period. The ARPES data indicate the presence of a surface electron accumulation layer.

Various models are considered for calculating the forces at the areas of contact of the satellite with the pinion gears of the planetary pinion gear (PPG). The distributions of forces along the pins for each model are given and an experiment is performed to check the reliability of the analytical dependences for different models. The applicability of these models for calculating the PPG is analyzed. Keywords: planetary pinion gearbox, load distribution, experiment. J.Sinitcyna@gmail.com

We show that in superlattices with a strong band inversion no hybridization gap exists. There are two points where the bands are crossing and the spectrum has a shape of Dirac cones. Due to the absence of the hybridization gap the optical absorption does not have a threshold and goes to zero gradually with the decrease of optical energy.

Realizing a large Landé g-factor of electrons in solid-state materials has long been thought of as a rewarding task as it can trigger abundant immediate applications in spintronics and quantum computing. Here, by using metamorphic InAsSb/InSb superlattices (SLs), we demonstrate an unprecedented high value of g ≈ 104, twice larger than that in bulk InSb, and fully spin-polarized states at low magnetic fields. In addition, we show that the g-factor can be tuned on demand from 20 to 110 via varying the SL period. The key ingredients of such a wide tunability are the wavefunction mixing and overlap between the electron and hole states, which have drawn little attention in prior studies. Our work not only establishes metamorphic InAsSb/InSb as a promising and competitive material platform for future quantum devices but also provides a new route toward g-factor engineering in semiconductor structures.