arXiv subjects

G. Cywinski

Publications and source records attributed to G. Cywinski.

5 recordsLinked to original sources

arXiv2026

Potential of Graphene/AlGaN/GaN heterostructures to study the drag and two-stream instability effects

Graphene/AlGaN/GaN heterostructures are proposed to investigate the drag and two-stream instability effects. In this study, graphene grown by chemical vapor deposition was transferred from copper onto the top of the standard AlGaN/GaN wafer, forming a heterostructure with two conducting layers separated by an AlGaN barrier layer. Contacts fabricated to the two-dimensional electron gas and graphene allowed us to study the drag current induced in graphene by passing the drive current through the two-dimensional electron gas. At low temperatures, the graphene drag current exhibited quantum oscillations as a function of the drive voltage. As temperature increases, quantum oscillations disappear, and the magnitude of the drag current increases. Graphene/AlGaN/GaN heterostructures are a promising platform for studying drag and two-stream instability effects, especially if the AlGaN barrier layer thickness can be reduced to a few nanometers.

cond-mat.mes-hall↗

arXiv2025

Effect of temperature on 2D terahertz plasmons and electron effective mass in AlGaN/GaN

The effect of temperature on two-dimensional plasmons in large-area AlGaN/GaN plasmonic crystals was studied experimentally. With the temperature increase the resonant plasmon frequency redshifts due to the strong temperature dependence of the electron effective mass and electron concentration under open to the environment surface of AlGaN. The temperature dependence of electron effective mass is confirmed by the cyclotron resonance measurements.

physics.optics↗

arXiv2021

Beatings of ratchet current magneto-oscillations in GaN-based grating gate structures: manifestation of spin-orbit band splitting

We report on the study of the magnetic ratchet effect in AlGaN/GaN heterostructures superimposed with lateral superlattice formed by dual-grating gate structure. We demonstrate that irradiation of the superlattice with terahertz beam results in the dc ratchet current, which shows giant magneto-oscillations in the regime of Shubnikov de Haas oscillations. The oscillations have the same period and are in phase with the resistivity oscillations. Remarkably, their amplitude is greatly enhanced as compared to the ratchet current at zero magnetic field, and the envelope of these oscillations exhibits large beatings as a function of the magnetic field. We demonstrate that the beatings are caused by the spin-orbit splitting of the conduction band. We develop a theory which gives a good qualitative explanation of all experimental observations and allows us to extract the spin-orbit splitting constant α_{\rm SO}= 7.5 \pm 1.5 meV \unicode{x212B}. We also discuss how our results are modified by plasmonic effects and show that these effects become more pronounced with decreasing the period of the gating gate structures down to sub-microns.

cond-mat.mes-hall↗

arXiv2003

Growth and properties of ferromagnetic In(1-x)Mn(x)Sb alloys

We discuss a new narrow-gap ferromagnetic (FM) semiconductor alloy, In(1-x)Mn(x)Sb, and its growth by low-temperature molecular-beam epitaxy. The magnetic properties were investigated by direct magnetization measurements, electrical transport, magnetic circular dichroism, and the magneto-optical Kerr effect. These data clearly indicate that In(1-x)Mn(x)Sb possesses all the attributes of a system with carrier-mediated FM interactions, including well-defined hysteresis loops, a cusp in the temperature dependence of the resistivity, strong negative magnetoresistance, and a large anomalous Hall effect. The Curie temperatures in samples investigated thus far range up to 8.5 K, which are consistent with a mean-field-theory simulation of the carrier-induced ferromagnetism based on the 8-band effective band-orbital method.

cond-mat.mtrl-sci↗

arXiv2003

In(1-x)Mn(x)Sb - a new narrow gap ferromagnetic semiconductor

A narrow-gap ferromagnetic In(1-x)Mn(x)Sb semiconductor alloy was successfully grown by low-temperature molecular beam epitaxy on CdTe/GaAs hybrid substrates. Ferromagnetic order in In(1-x)Mn(x)Sb was unambiguously established by the observation of clear hysteresis loops both in direct magnetization measurements and in the anomalous Hall effect, with Curie temperatures T_C ranging up to 8.5 K. The observed values of T_C agree well with the existing models of carrier-induced ferromagnetism.

cond-mat.mtrl-sci↗