arXiv subjects

G. Ausanio

Publications and source records attributed to G. Ausanio.

3 recordsLinked to original sources

arXiv2026

Phase dynamics and dissipation in tunnel ferromagnetic Josephson junctions

We investigate tunnel ferromagnetic Josephson junctions based on Superconductor-Insulator-thin superconductor-Ferromagnet-Superconductor multilayers. A comparative study of their electrodynamic properties is performed for junctions with niobium and aluminum (Al) electrodes, featuring different ferromagnetic interlayer materials and lateral dimensions ranging from the micrometric to the submicrometric scale. The parameters extracted from the fitting of the current-voltage characteristics using the tunnel junction microscopic model are found to be consistent with those independently estimated from switching current distribution measurements. Submicrometric Al-based devices exhibit electrodynamic properties comparable to those implemented in state-of-the-art transmon qubits and display clear signatures of quantum phase diffusion. The strong agreement between transport modelling and escape dynamics establishes a robust framework for describing hybrid ferromagnetic Josephson junctions consistent with their energy scales and supports their potential integration into superconducting quantum and classical digital circuits.

cond-mat.supr-con↗

arXiv2006

Zero-Dimensional Superconducting Fluctuations and Fluctuating Diamagnetism in Lead Nanoparticles

High resolution SQUID magnetization measurements in lead nanoparticles are used to study the fluctuating diamagnetism in zero-dimensional condition, namely for particle size d lesser than the coherence length. The diamagnetic magnetization Mdia (H, T= const) as a function of the field H at constant temperature is reported in the critical region and compared with the behaviour in the temperature range where the first-order fluctuation correction is expected to hold. The magnetization curves are analysed in the framework of exact fluctuation theories based on the Ginzburg-Landau functional for the coherence length much greater than d. The role of the upturn field Hup where Mdia reverses the field dependence is discussed and its relevance for the study of the fluctuating diamagnetism, particularly in the critical region where the first-order fluctuation correction breaks down, is pointed out. The size and temperature dependence of Hup is theoretically derived and compared to the experimental data. The relevance and the magnetization curves for non-evanescent field and of the upturn field for the study of the fluctuating diamagnetism above the superconducting transition temperature is emphasized.

cond-mat.supr-con↗

arXiv2001

Electrodynamic response of MgB2 sintered pellets and thin films

We present a study of the electrodynamic response of MgB2 pellets and thin film samples exhibiting critical temperatures ranging between 26 and 38 K. We have performed accurate measurements of the surface impedance ZS =RS+iXS as a function of the temperature and of the magnitude of the electromagnetic field. The temperature variation and the field dependence of ZS was measured by a dielectric resonator cavity technique in the microwave region. In particular, the temperature variation of the magnetic penetration depth was also determined in the RF region by a single coil mutual inductance method. In the case of the films, for T<TC/2 a clear exponential behavior of the penetration depth is observed, which can be explained by a simple BCS s-wave model with a reduced value of the energy gap. On the contrary, pellets show no evidence of saturation, and the experimental results strictly follow a quadratic dependence down to the lowest temperatures. This behavior can be induced by the presence of metallic Mg inclusions that may locally depress the gap. The analysis of the field dependence of the surface impedance in the microwave region confirms that the electrodynamic response of MgB2 is dominated by different sources of dissipation, depending on the sample history, likely to be ascribed to the predominance of grain boundaries or normal regions on its surface.

cond-mat.supr-con↗