Current-induced highly dissipative domains in high Tc thin films

We have investigated the resistive response of high Tc thin films submitted to a high density of current. For this purpose, current pulses were applied into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the time dependent voltage, we observe that at a certain critical current j*, a highly dissipative domain develops somewhere along the bridge. The successive formation of these domains produces stepped I-V characteristics. We present evidences that these domains are not regions with a temperature above Tc, as for hot spots. In fact this phenomenon appears to be analog to the nucleation of phase-slip centers observed in conventional superconductors near Tc, but here in contrast they appear in a wide temperature range. Under some conditions, these domains will propagate and destroy the superconductivity within the whole sample. We have measured the temperature dependence of j* and found a similar behavior in the two investigated compounds. This temperature dependence is just the one expected for the depairing current, but the amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.

Complete microwave characterization at 36 GHz of YBaCuO thin films deposited on MgO substrates. Influence of the substrate preparation

This paper deals with the determination of $\lambda$ and Z$_s$ of YBa$_2$Cu$_3$O$_{7-\delta}$ thin films deposited on MgO singlecrystals, from 36 GHz resonant conical cavity measurements performed in the 25 K to 300 K temperature range. The results are discussed in relation with DC electrical transport properties of the films and also with substrate preparation prior to YBaCuO deposition

Dynamic electrical response of YBaCuO thin films as a function of microstructure in view of applications to agile electronics

The electrical characteristics of YBaCuO thin films sputtered on LaAlO3 and MgO single-crystal substrates have been measured using a pulsed current technique, to avoid ohmic heating effects. The results are discussed in relation with deposition temperature (for films deposited on LaAlO3) and substrate preparation (for films deposited on MgO). In the latter case, results are also discussed in the framework of a statistical model, which provides an empirical approach for the pinning phenomena in YBaCuO films, when a static magnetic field is applied

Low frequency noise in YBaCuO superconducting thin films deposited on MgO

In this paper we present a comparison of DC and electrical noise characteristics of high-temperature superconducting thin films. Two YBaCuO thin films deposited on MgO substrates were studied and compared. The R-T, I-V and electrical noise properties were studied for each film. Noise measurements show that they are more sensitive than the DC ones. They can give evidence of physical phenomena such as “pre-transitional superconducting effect

High-Tc superconducting microbolometer for terahertz applications

Superconducting hot electron bolometer mixers are now a competitive alternative to Schottky diode mixers in the terahertz frequency range because of their ultra wideband (from millimeter waves to visible light), high conversion gain, and low intrinsic noise level. High Tc superconductor materials can be used to make hot electron bolometers and present some advantage in term of operating temperature and cooling. In this paper, we present first a model for the study of superconducting hot electron bolometers responsivity in direct detection mode, in order to establish a firm basis for the design of future THz mixers. Secondly, an original process to realize YBaCuO hot electron bolometer mixers will be described. Submicron YBaCuO superconducting structures are expitaxially sputter deposited on MgO substrates and patterned by using electron beam lithography in combination with optical lithography. Metal masks achieved by electron beam lithography are insuring a good bridge definition and protection during ion etching. Finally, detection experiments are being performed with a laser at 850 nm wavelength, in homodyne mode in order to prove the feasibility and potential performances of these devices

Influence of thermal annealing of MgO substrate on 1/f noise of YBaCuO superconducting thin films

In this work, we have characterized three NbNx thin films deposited on sapphire substrate and compared their noise properties. The three films were measured in the same conditions. In the first time, the films were characterized with an impedance analyzer from 20 Hz to 1 MHz. The films are then considered as a RC dipole with a resistor R in parallel with a capacitor C. With the Nyquist formula, we calculate the noise voltage spectral density SvTh of the RC dipole considering that only the resistor R exhibits thermal noise in unbiased samples. In the second time, noise measurements were made with the samples biased. Thanks to a four contacts configuration, we checked that contact noise do not contribute to our measurements. The difference between the measured noise and the calculated thermal noise SvTh shows an extra 1/f noise without GR noise contributions. The 1/f noise in the three films extra noise is compared. These results are also compared to the noise measured on NbN thin films deposited on silicon substrate [1]

Centrosomal cohesion deficits as cellular biomarker in lymphoblastoid cell lines from LRRK2 Parkinson's disease patients

Leucine-rich repeat kinase 2 (LRRK2) is a promising therapeutic target for the treatment of Parkinson's disease (PD), and orally bioavailable, brain penetrant and highly potent LRRK2 kinase inhibitors are in early stages of clinical testing. Detection of LRRK2 phosphorylation, as well as phosphorylation of Rab10, a LRRK2 kinase substrate, have been proposed as target engagement biomarkers for LRRK2 inhibitor clinical trials. However, these readouts do not seem able to stratify patients based on enhanced LRRK2 kinase activity. Here, we describe a robust cell biological assay based on centrosomal cohesion alterations which were observed in peripheral blood mononuclear cellderived lymphoblastoid cell lines (LCLs) from patients with G2019S LRRK2 mutations as compared with healthy controls, and could also be detected in a subset of sporadic PD patient samples. We suggest that LCLs may be a valuable resource for LRRK2 research, and that determination of centrosomal cohesion deficits may assist in the stratification of a subset of sporadic PD patients.This work was supported by funding from the Michael J. Fox Foundation for Parkinson's Research (U.S.A.), FEDER, the Spanish Ministry of Science, Innovation and Universities (SAF2017-89402-R), and by the French Ministry of Health's PHRC program (CONVERGENCE 2008-A00219-42), the University of Lille, Inserm and the Lille University Hospital