Probing transport mechanisms of BaFe2As2 superconducting films and grain boundary junctions by noise spectroscopy

Rotzinger

Mauro

et al. 2018

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Granular aluminum oxide is an attractive material for superconducting quantum electronics. However, its low-temperature normal state transport properties are still not fully understood, while they could be related to the unconventional phenomenon of the superconductivity in this material. In order to obtain useful information on this aspect, a detailed study of charge carrier fluctuations has been performed in granular aluminum oxide films. The results of electric noise measurements indicate the presence of a Kondo-type spin-flip scattering mechanism for the conducting electrons in the normal state, at low temperatures. Moreover, the magnetic field dependence of the noise amplitude suggests that interface magnetic moments are the main source of fluctuations. The identification of the nature of fluctuation processes is a mandatory requirement for the improvement of quality and performance of quantum devices.

Section: Introductionmentioning

confidence: 99%

Kondo-like transport and magnetic field effect of charge carrier fluctuations in granular aluminum oxide thin films

Rotzinger

Mauro

et al. 2018

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“…The mechanism of phase slippage 1 9 10 and related concept of kinematic vortex 11 12 , previously introduced to account for transport properties of micro-bridges and whiskers, has gained a renewed interest also in the explanation of transport properties of plain thin superconducting films at mesoscale 13 14 15 16 17 18 (with or without holes) and nanowires 19 20 21 22 23 . The same mechanism could play an important role in the dynamics of iron-based superconducting grain boundary junctions, where the presence of weak links has been identified through noise spectroscopy 24 . Moreover, nano-fabrication techniques also permitted to revisit the physics of proximity effect 25 between a superconducting material and a non superconducting material and related Josephson effects 26 in lateral weak links 27 at mesoscale.…”

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confidence: 90%

Current driven transition from Abrikosov-Josephson to Josephson-like vortex in mesoscopic lateral S/S’/S superconducting weak links

Carapella

Sabatino

et al. 2016

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Vortices are topological defects accounting for many important effects in superconductivity, superfluidity, and magnetism. Here we address the stability of a small number of such excitations driven by strong external forces. We focus on Abrikosov-Josephson vortex that appears in lateral superconducting S/S’/S weak links with suppressed superconductivity in S’. In such a system the vortex is nucleated and confined in the narrow S’ region by means of a small magnetic field and moves under the effect of a force proportional to an applied electrical current with a velocity proportional to the measured voltage. Our numerical simulations show that when a slow moving Abrikosov-Josephson vortex is driven by a strong constant current it becomes unstable with respect to a faster moving excitation: the Josephon-like vortex. Such a current-driven transition explains the structured dissipative branches that we observe in the voltage-current curve of the weak link. When vortex matter is strongly confined phenomena as magnetoresistance oscillations and reentrance of superconductivity can possibly occur. We experimentally observe these phenomena in our weak links.

“…Among the available non-destructive characterization techniques, noise spectroscopy has demonstrated its effectiveness in the investigation of advanced photovoltaic and innovative materials 18 19 20 21 . Preliminary characterizations have also been performed in mesoscopic perovskite photodiodes 22 .…”

mentioning

confidence: 99%

Unravelling the low-temperature metastable state in perovskite solar cells by noise spectroscopy

Lang

Mauro

et al. 2016

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The hybrid perovskite methylammonium lead iodide CH3NH3PbI3 recently revealed its potential for the manufacturing of low-cost and efficient photovoltaic cells. However, many questions remain unanswered regarding the physics of the charge carrier conduction. In this respect, it is known that two structural phase transitions, occurring at temperatures near 160 and 310 K, could profoundly change the electronic properties of the photovoltaic material, but, up to now, a clear experimental evidence has not been reported. In order to shed light on this topic, the low-temperature phase transition of perovskite solar cells has been thoroughly investigated by using electric noise spectroscopy. Here it is shown that the dynamics of fluctuations detect the existence of a metastable state in a crossover region between the room-temperature tetragonal and the low-temperature orthorhombic phases of the perovskite compound. Besides the presence of a noise peak at this transition, a saturation of the fluctuation amplitudes is observed induced by the external DC current or, equivalently, by light exposure. This noise saturation effect is independent on temperature, and may represent an important aspect to consider for a detailed explanation of the mechanisms of operation in perovskite solar cells.