arXiv subjects

S. L. Prischepa

Publications and source records attributed to S. L. Prischepa.

9 recordsLinked to original sources

arXiv2014

Superconducting nanowire quantum interference device based on Nb ultrathin films deposited on self-assembled porous Si templates

Magnetoresistance oscillations were observed on networks of superconducting ultrathin Nb nanowires presenting evidences of either thermal or quantum activated phase slips. The magnetic transport data, discussed in the framework of different scenarios, reveal that the system behaves coherently in the temperature range where the contribution of the fluctuations is important.

cond-mat.supr-con↗

arXiv2014

Conductance spectroscopy in ferromanget/superconductor hybrids

We present theoretical model for the proximity effect in F-SFF-F structures (F is ferromagnet, S is superconductor) with non-collinear magnetizations vectors in the F-layers and with arbitrary magnitudes of exchange fields. Electrical conductance of these structures is analyzed within the Keldysh-Usadel formalism in the diffusive regime as a function of a misorientation angle between magnetizations of the F-layers and transparencies of SF and FF interfaces. We show that long-range triplet superconducting correlations manifest themselves either as a zero-bias peak in the case of perfect transparency of FF interface, or as a two-peak structure in the case of finite transparency. The predicted features may serve as a diagnostic tool for characterization of interfaces in superconducting hybrid structures

cond-mat.supr-con↗

arXiv2013

Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

We report on the transport properties of an array of N about 30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V(I) characteristics as a function of H which can be both consistently described by quantum tunneling of phase slips.

cond-mat.supr-con↗

arXiv2012

Quantum phase slips in superconducting Nb nanowire networks deposited on self-assembled Si templates

Robust porous silicon substrates were employed for generating interconnected networks of superconducting ultrathin Nb nanowires. Scanning electron microscopy analysis was performed to investigate the morphology of the samples, which constitute of polycrystalline single wires with grain size of about 10 nm. The samples exhibit nonzero resistance over a broad temperature range below the critical temperature, fingerprint of phase slippage processes. The transport data are satisfactory reproduced by models describing both thermal and quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires.

cond-mat.supr-con↗

arXiv2009

Evidence of fractional matching states in nanoperforated Nb thin film grown on porous silicon

Resistive transitions have been measured on a perforated Nb thin film with a lattice of holes with the period of the order of ten nanometers. Bumps in the dR/dH versus H curves have been observed at the first matching field and its fractional values, 1/4, 1/9 and 1/16. This effect has been related to different vortex lattice configurations made available by the underlying lattice of holes.

cond-mat.supr-con↗

arXiv2008

Superconducting properties of Nb thin films deposited on porous silicon templates

Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering on the porous Si substrates, inherited their structure made of holes of 5 or 10 nm diameter and of 10 to 40 nm spacing, which provide an artificial pinning structure. The superconducting properties were investigated by transport measurements performed in the presence of magnetic field for different film thickness and substrates with different interpore spacing. Perpendicular upper critical fields measurements present peculiar features such as a change in the H_c2(T) curvature and oscillations in the field dependence of the superconducting resistive transition width at H=1 Tesla. This field value is much higher than typical matching fields in perforated superconductors, as a consequence of the small interpore distance.

cond-mat.supr-con↗

arXiv2004

Interface Transparency of Nb/Pd Layered Systems

We have investigated, in the framework of proximity effect theory, the interface transparency T of superconducting/normal metal layered systems which consist of Nb and high paramagnetic Pd deposited by dc magnetron sputtering. The obtained T value is relatively high, as expected by theoretical arguments. This leads to a large value of the ratio $d_{s}^{cr}/ ξ_{s}$ although Pd does not exhibit any magnetic ordering.

cond-mat.supr-con↗

arXiv2001

Scaling of H_{c2 \perp}(T) in Nb/CuMn Multilayers

Measurements of the perpendicular upper critical magnetic field H_{c2 \perp}(T) are reported for several Nb/CuMn multilayers. It is found that, despite the magnetic nature of the samples, the data for samples with low Mn percentage in the CuMn layers are simply described by the Werthamer-Helfand-Honenberg theory for conventional type-II superconductors, neglecting both Pauli spin paramagnetism and spin orbit impurity scattering. For high Mn concentration a different theoretical aprroach is needed.

cond-mat.supr-con↗

arXiv2000

Irreversibility Line in Nb/CuMn Multilayers with a Regular Array of Antidots

The transport properties of Nb/CuMn multilayers with a regular array of electron beam lithography obtained antidots have been measured at different temperatures in the presence of external perpendicular magnetic fields. Hysteretical I-V characteristics have been observed which disappear when approaching the upper critical magnetic field curve H_{c2}(T). Comparing these data with other results (Arrhenius plots of resistive transition curves, logV-logI characteristics) we have been able to relate the onset of the hysteresis to the presence of an irreversibility line. We discuss several possible mechanisms to clarify the nature of this line. Among them the most plausible seems to be the vortex melting mainly induced by quantum fluctuations.

cond-mat.supr-con↗