Searcharxiv⌕ Search

arXiv subjects

E. Sarnelli

Publications and source records attributed to E. Sarnelli.

8 recordsLinked to original sources
arXiv2022

Proton induced Dark Count Rate degradation in 150-nm CMOS Single-Photon Avalanche Diodes

Proton irradiation effects on a Single-Photon Avalanche Diodes (SPADs) device manufactured using a 150-nm CMOS process are presented. An irradiation campaign has been carried out with protons of 20 MeV and 24 MeV on several samples of a test chip containing SPADs arrays with two different junction layouts. The dark count rate distributions have been analyzed as a function of the displacement damage dose. Annealing and cooling have been investigated as possible damage mitigation approaches. We also discuss, through a space radiation simulation, the suitability of such devices on several space mission case-studies.

physics.ins-det↗
arXiv2017

Current Induced Resistive State in Fe(Se,Te) Superconducting Nanobridges

We study the current-voltage characteristics of Fe(Se,Te) thin films deposited on CaF$_2$ substrates in form of nanostrips (width $w\simλ$, $λ$ the London penetration length). In view of a possible application of these materials to superconductive electronics and micro-electronics we focus on transport properties in small magnetic field, the one generated by the bias current. From the characteristics taken at different temperatures we derive estimates for the pinning potential $U$ and the pinning potential range $δ$. Since the sample lines are very narrow, the classical creep flow model provides a sufficiently accurate interpretation of the data only when the attractive interaction between magnetic flux lines of opposite sign is taken into account. The observed voltages and the induced detriment of the critical current of the nanostrips are compatible with the presence of few tens of magnetic field lines at the equilibrium and a strongly inhomogeneous current density distribution. In particular, we argue that the sharp corners defining the bridge geometry represent points of easy magnetic flux lines injection. The results are relevant for creep flow analysis in superconducting Fe(Se,Te) nanostrips.

cond-mat.supr-con↗
arXiv2013

πstates in all-pnictide Josephson junctions

We study the Josephson effect in $s_{\pm}/I/s_{\pm}$ junctions made by two bands reversed sign s-wave ($s_{\pm}$) superconductive materials. We derive an equation providing the bound Andreev energy states parameterized by the band ratio $α$, a parameter accounting for the weight of the second band with respect to the first one at the interface. For selected values of the band ratio and tunnel barrier amplitude, we predict various features of the Josephson current, among which a possible high temperature $π$ state of the junction (a doubly degenerate junction ground state) and a $π\rightarrow 0$ crossover with decreasing temperature.

cond-mat.supr-con↗
arXiv2009

Two-stage dissipation in a superconducting microbridge: Experiment and modeling

Using fluorescent microthermal imaging we have investigated the origin of "two-step" behavior in I-V curves for a current-carrying YBa_2Cu_3O_x superconducting bridge. High resolution temperature maps reveal that as the applied current increases the first step in the voltage corresponds to local dissipation (hot spot), whereas the second step is associated with onset of global dissipation throughout the entire bridge. A quantitative explanation of the experimental results is provided by a simple model for an inhomogeneous superconductor, assuming that the hot spot nucleates at a location with slightly depressed superconducting properties.

cond-mat.supr-con↗
arXiv2007

Resonance phenomena in asymmetric superconducting quantum interference devices

Theory of self induced resonances in asymmetric two-junction interferometer device is presented. In real devices it is impossible to have an ideal interferometer free of imperfections. Thus, we extended previous theoretical approaches introducing a model which contains several asymmetries: Josephson current $ε$, capacitances $χ$ and dissipation $ρ$ presented in an equivalent circuit. Moreover, non conventional symmetry of the order parameter in high temperature superconducting quantum interference devices forced us to include phase asymmetries. Therefore, the model has been extended to the case of $π$-shift interferometers, where a phase shift is present in one of the junctions.

cond-mat.supr-con↗
arXiv2003

Direct Observation of a Temperature Dependent 0-pi Junction Transition in a Mesoscopic High Critical Temperature Grain Boundary Junction

We have observed, for the first time, a temperature dependent 0-pi junction crossover in a 45 symmetric [001] tilt grain boundary junction. Experimental data, obtained by a double phase-sensitive test based on a low inductance dc SQUID, show an anomalous nonmonotonic temperature dependence of the Josephson current, clear evidence of a critical current sign change at a temperature T*. At the same temperature, the SQUID undergoes a transition from a 0-SQUID to a pi-SQUID. Results are in good agreement with theoretical models taking into account mid-gap states in low transparency junctions.

cond-mat.supr-con↗
arXiv2000

Feasibility of biepitaxial YBaCuO Josephson junctions for fundamental studies and potential circuit implementation

We present various concepts and experimental procedures to produce biepitaxial YBaCuO grain boundary Josephson junctions. The device properties have an interesting phenomenology related in part to the possible influence of "pai loops". The performance of our junctions and Superconducting Quantum Interference Devices indicates significant improvement in the biepitaxial technique. Further, we propose methods for fabricating circuits in which "0-" and "pai-loops" are controllably located on the same chip.

cond-mat.supr-con↗