Search

We report on superconducting properties of a novel material: rhenium-lutetium films. Different compositions of Re x Lu binary are explored from x ≈ 3.8 to close to pure Re stoichiometry. The highest critical temperature, up to T c ≈ 7 K, is obtained for x ≈ 10.5 in accordance with electron dispersive spectroscopy results. Depending on the deposition conditions, polycrystalline or amorphous films are obtainable, both of which are interesting for practical use. Crystalline structure of polycrystalline phase is identified as a non-centrosymmetric superconductor using grazing incidence x-ray diffractometry. Superconducting properties were characterized both resistively and magnetically. Magnetoresistivity and AC/DC susceptibility measurements allowed us to determine H c 1 and H c 2 of these films, as well as estimate coherence length ξ (0) and magnetic penetration depth λ L (0) . We also provide information on surface morphology of these films. Demonstration of superconductivity in this material justifies the point of view that Lu plays a role of group 3 transition metal in period 6 of the Periodic table of elements. Then, in analogy with Re–Nb, Re–Ti, Re–Hf and Re–Zr, one can expect that crystalline Re–Lu also breaks time-reversal symmetry. If that is proven by future experiments, in combination with noncentrosymmetric feature, these films could be used for forming nonreciprocal current devices, such as superconducting diodes, without involvement of external magnetic fields. [ABSTRACT FROM AUTHOR]

Research involving use of superconductors with Cooper condensates in triplet pairing states for development of quantum computers is described and discussed.

Research describing single photon sensors is presented. In particular the properties of superconducting quantum interference device array amplifiers coupled to detector pixels are investigated.

Laser deposition methods of large area thin films are reported and obtained films were tested and optical density measured.

Research was conducted to examine imaging detectors based on the response of anisotropic layered materials. The inherent characteristics of naturally layered materials such as the high-temperature superconductors cause a transient voltage when a light pulse is absorbed. The amplitude is proportional to the absorbed energy. A phenomenological model of the effects consistent with observations on the first generation of sensors is presented.

Perfect screening of sub-milligauss magnetic fields (ideal diamagnetism) by a system comprised of a graphene and thin permalloy foil parallel to the graphene layer immersed in n -heptane is observed at room temperature. The presence of all three components is necessary for the effect to occur. Ideal diamagnetic response appears at the moment of n -heptane injection and disappears when the liquid evaporates. Until then, no change of diamagnetic moment occurs at further variation of the field. The observed ideal diamagnetic feature is either a footprint of a novel type of superconductivity at room temperature or a yet unknown quantum phenomenon in condensed matter physics. [ABSTRACT FROM AUTHOR]

In nonequilibrium states, the entropy is reduced from its maximum thermodynamic equilibrium value by virtue of an external energy supply. Such states are characterized by a higher ordering compared to the equilibrium. Human beings represent the highest level of nonequilibrium state, at least in the known part of the Universe. Other physical systems are also well-known, for example, quantum generators, e.g., lasers. Their operation requires a high level of deviation from equilibrium called inverse population. In turn, states out of equilibrium require energy influx for their maintenance, i.e., they should be open systems. In this short review we describe in the form of dialogue between Prof. A. M. Gulian and his younger colleagues Dr. Rajendra Dulal, Dr. Serafim Teknowijoyo and Dr. Sara Chahid the task of achieving inverse population in superconductors. Then, the dialogue moves towards experimental consequences that nonequilibrium superconductors can yield. These include topics related with deeper understanding of mechanisms of superconductivity in novel materials, in particular related to the "glue" which pairs electrons in Cooper pairs. Such understanding will facilitate development of Bose-field quantum generators like lasers, and coherent acoustic as well as paramagnon quantum sources, none of which are yet realized in nonequilibrium superconductors. [ABSTRACT FROM AUTHOR]

Studies of the Abrikosov vortex motion in superconductors based on time-dependent Ginzburg–Landau equations reveal an opportunity to detect the values of the Aharonov–Bohm type curl-less vector potentials without closed-loop electron trajectories encompassing the magnetic flux. [ABSTRACT FROM AUTHOR]

Using finite gap, time-dependent Ginzburg–Landau equations, generalized to include non-thermal phonons, we report numerical simulations of vortex nucleation, propagation, and annihilation in thin, finite strips of magnetic-impurity free, perfectly homogeneous superconductors. When a steady electric current passes through the strip with either surface defects or nonequilibrium phonon sources ( e.g. , local “hotspots”), periodic vortex generation and annihilation is observed even in the absence of external magnetic fields. Local pulses of electric field are produced upon annihilation. The injected phonon lines steer the vortices during their motion within the strip, potentially allowing control of the annihilation site. [ABSTRACT FROM AUTHOR]