Multivalued current-phase relationship in a.c. Josephson effect for a three-dimensional Weyl semimetal WTe2_2

We experimentally study electron transport between two superconducting indium leads, coupled to a single WTe$_2$ crystal, which is a three-dimensional Weyl semimetal. We demonstrate Josephson current in long 5~$\mu$m In-WTe$_2$-In junctions, as confirmed by the observation of integer (1,2,3) and fractional (1/3, 1/2, 2/3) Shapiro steps under microwave irradiation. Demonstration of fractional a.c. Josephson effect indicates multivalued character of the current-phase relationship, which we connect with Weyl topological surface states contribution to Josephson current. In contrast to topological insulators and Dirac semimetals, we do not observe $4\pi$ periodicity in a.c. Josephson effect for WTe$_2$ at different frequencies and power, which might reflect chiral character of the Fermi arc surface states in Weyl semimetal.Comment: the text is seriously corrected. arXiv admin note: text overlap with arXiv:1801.0955

Multiple magnon modes in the Co3_3Sn2_2S2_2 Weyl semimetal candidate

We experimentally investigate electron transport in kagome-lattice ferromagnet Co$_3$Sn$_2$S$_2$, which is regarded as a time-reversal symmetry broken Weyl semimetal candidate. We demonstrate $dV/dI(I)$ curves with pronounced asymmetric $dV/dI$ spikes, similar to those attributed to current-induced spin-wave excitations in ferromagnetic multilayers. In contrast to multilayers, we observe several $dV/dI$ spikes' sequences at low, $\approx$10$^4$ A/cm$^2$, current densities for a thick single-crystal Co$_3$Sn$_2$S$_2$ flake in the regime of fully spin-polarized bulk. The spikes at low current densities can be attributed to novel magnon branches in magnetic Weyl semimetals, which are predicted due to the coupling between two magnetic moments mediated by Weyl fermions. Presence of spin-transfer effects at low current densities in Co$_3$Sn$_2$S$_2$ makes the material attractive for applications in spintronics.Comment: final versio

Conductance oscillations and zero-bias anomaly in a single superconducting junction to a three-dimensional Bi2Te3Bi_2Te_3 topological insulator

We experimentally investigate Andreev transport through a single junction between an s-wave indium superconductor and a thick film of a three-dimensional $Bi_2Te_3$ topological insulator. We study $Bi_2Te_3$ samples with different bulk and surface characteristics, where the presence of a topological surface state is confirmed by direct ARPES measurements. All the junctions demonstrate Andreev transport within the superconducting gap. For junctions with transparent $In-Bi_2Te_3$ interfaces we find a number of nearly periodic conductance oscillations, which are accompanied by zero-bias conductance anomaly. Both effects disappear above the superconducting transition or for resistive junctions. We propose a consistent interpretation of both effects as originating from proximity-induced superconducting correlations within the $Bi_2Te_3$ topological surface state

Signature of Fermi arc surface states in Andreev reflection at the WTe2_2 Weyl semimetal surface

We experimentally investigate charge transport through the interface between a niobium superconductor and a three-dimensional WTe$_2$ Weyl semimetal. In addition to classical Andreev reflection, we observe sharp non-periodic subgap resistance resonances. From an analysis of their positions, magnetic field and temperature dependencies, we can interpret them as an analog of Tomasch oscillations for transport along the topological surface state across the region of proximity-induced superconductivity at the Nb-WTe$_2$ interface. Observation of distinct geometrical resonances implies a specific transmission direction for carriers, which is a hallmark of the Fermi arc surface states.Comment: 5 pages, some misprints has been correcte

Signature of Fermi arc surface states in Andreev reflection at the WTe2_2 Weyl semimetal surface

We experimentally investigate charge transport through the interface between a niobium superconductor and a three-dimensional WTe$_2$ Weyl semimetal. In addition to classical Andreev reflection, we observe sharp non-periodic subgap resistance resonances. From an analysis of their positions, magnetic field and temperature dependencies, we can interpret them as an analog of Tomasch oscillations for transport along the topological surface state across the region of proximity-induced superconductivity at the Nb-WTe$_2$ interface. Observation of distinct geometrical resonances implies a specific transmission direction for carriers, which is a hallmark of the Fermi arc surface states.Comment: 5 pages, some misprints has been correcte

Magnetically stable zero-bias anomaly in Andreev contact to the magnetic Weyl semimetal Co3_3Sn2_2S2_2

Being encouraged by the interplay between topology, superconductivity and magnetism, we experimentally investigate charge transport through the interface between the Nb superconductor and the time-reversal symmetry breaking Weyl semimetal Co$_3$Sn$_2$S$_2$. In addition to the proximity induced superconducting gap, we observe several subgap features, among which the most interesting is the prominent subgap zero-bias anomaly, absolutely stable against external magnetic fields up to the critical field of Nb. As the promising scenario for the zero-bias anomaly to appear in transport characteristics, we consider the proximity induced zero-energy Andreev bound states interfaced with the half-metallic Co$_3$Sn$_2$S$_2$ and influenced by the strong spin-orbit coupling and large Zeeman splitting

Study of the Forces Acting on the Animal in the Installation for Fixing with Veterinary Treatments

The study of the forces acting on the animal in the installation for fixing with veterinary treatments. The most time consuming processes in service animals are zootechnical and veterinary treatment of sheep. During the year, it is necessary to carry out more than ten such treatments of each animal, which requires a lot of labor. Almost all animal treatments such as feed to the operator’s workplace and their fixation in a convenient position for him requires significant physical effort of the operator. Therefore, today the technologies and technical means should be created to reduce labor costs for various treatments. The relevance of the problem is due to the lack of theoretical foundations and experimental data for the creation of technological equipment for fixing sheep in zootechnical and veterinary treatments. The purpose of the study is the theoretical and experimental justification of the installation for fixing sheep in zootechnical and veterinary treatments with the justification of the existing efforts on the animal, excluding injury. Developed installation and presented a scheme with two of the conveyor belts forming the grooved shape When designing the installation, the main focus was on the justification of structural elements and modes of operation from the viewpoint of eliminating the possibility of injury to the animal. The experimental studies have confirmed the correctness of the obtained analytical dependences. The obtained results will enable designers to create equipment for the fixation of sheep at the zootechnical and veterinary treatments, precluding injury to the animal and reducing labor costs