Zero-Dimensional Superconducting Fluctuations and Fluctuating Diamagnetism in Lead Nanoparticles

TL;DR

This paper investigates the fluctuating diamagnetism in lead nanoparticles under zero-dimensional conditions using high-resolution SQUID magnetization measurements, analyzing the behavior near the superconducting transition with fluctuation theories.

Contribution

It provides a detailed experimental and theoretical analysis of fluctuating diamagnetism in lead nanoparticles, especially focusing on the upturn field and its size and temperature dependence.

Findings

The magnetization behavior aligns with fluctuation theories based on Ginzburg-Landau functional.

The size and temperature dependence of the upturn field Hup are theoretically derived and experimentally confirmed.

The study highlights the significance of the upturn field in understanding fluctuating diamagnetism above Tc.

Abstract

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.