Fano effect in Aharonov–Bohm ring with topologically superconducting bridge
The review discusses properties of superconducting phases with a nontrivial topology and conditions for their implementation in condensed matter, criteria for the appearance of the Majorana-type elementary excitations in solids, as well as principles and experimental methods for identifying Majorana bound states (MBSs). Along with the well-known models of the Kitaev chain and superconducting nanowire (SW) with spin-orbit interaction in an external magnetic ﬁeld, models of quasi-two-dimensional materials in which MBSs are realized in the presence of noncollinear spin ordering are considered. For the ﬁnite-length SW, a cascade of quantum transitions with a magnetic-ﬁeld change is demonstrated, accompanied by a change in the fermionic parity of the ground state. The anomalous behavior of the magnetocaloric eﬀect that occurs in this case can be used to probe MBSs. Considerable attention is paid to the analysis of transport characteristics of devices containing materials with non-trivial topology. The results of studying the conductance of Aharonov-Bohm ring that arms are connected by the SW are presented in detail. An important feature of this device is the appearance of Fano resonances in the magnetic-ﬁeld dependence of the conductance when the SW is in the topologically nontrivial phase. A relationship has been established between the characteristics of such resonances and the spatial structure of the SW state with the lowest energy. Within the framework of the t-J-V model on a triangular lattice, the conditions for the MBS appearance in the phase of coexistence of chiral d + id superconductivity and 120-degree spin ordering are determined. When electron-electron interactions are taken into account, topological invariants of low-dimensional superconducting materials with noncollinear spin ordering are considered. The formation of Majorana modes in regions with an odd value of the topological Z-invariant is demonstrated. The spatial structure of these excitations in the ensemble of Hubbard fermions is determined.
We report an experimental observation of superconductivity in Cd3As2 thin films without application of external pressure. The films under study were synthesized by magnetron sputtering. Surface studies suggest that the observed transport characteristics are related to the polycrystalline continuous part of the investigated films with a homogeneous distribution of elements and the Cd-to-As ratio close to stoichiometric Cd3As2. The latter is also supported by Raman spectra of the studied films where two pronounced peaks inherent to Cd3As2 were observed. The obtained x-ray diffraction patterns for studied films also correspond to the Cd3As2 lattice. The formation of a superconducting phase in the films under study is confirmed by the characteristic behavior of the temperature and the magnetic field dependence of the sample resistivity, as well as by the presence of pronounced zero-resistance plateaus in the dV/dI characteristics. The corresponding H-c-T-c plots reveal a clearly pronounced linear behavior within the intermediate temperature range, similar to that observed for bulk Cd3As2 and Bi2Se3 films under pressure, suggesting the possibility of a nontrivial pairing in the films under investigation. We discuss a possible role of the sample inhomogeneities and crystal strains in the observed phenomena.
We experimentally study lateral electron transport between two 5−μm-spaced superconducting indium leads on a top of magnetic Weyl semimetal Co3Sn2S2. For the disordered magnetic state of Co3Sn2S2 crystal, we observe only the Andreev reflection in the proximity of each of the leads, which is indicative of highly transparent In-Co3Sn2S2 interfaces. If the sample is homogeneously magnetized, it demonstrates a well-developed anomalous Hall effect state. In this regime we find the Josephson current that takes place even for 5−μm-long junctions and show the unusual magnetic field and temperature dependencies. As a possible reason for the results obtained, we discuss the contribution to the proximity-induced spin-triplet Josephson current from the topologically protected Fermi-arc states on the surface of Co3Sn2S2.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.