Experimental observation of high field diamagnetic fluctuations in Niobium

TL;DR

This study investigates high-field diamagnetic fluctuations in niobium, revealing broadening of the superconducting transition under magnetic fields and testing the applicability of Landau level fluctuation theory.

Contribution

It provides experimental evidence of Landau level fluctuation effects in niobium and compares these with high-temperature superconductors, exploring universality.

Findings

Superconducting transition broadens with increasing magnetic field.

Scaling analysis aligns with $H_{c2}(T)$ but shows no universal 3D LLL behavior.

Data supports Landau level fluctuation theory in niobium.

Abstract

We have performed a magnetic study of a bulk metallic sample of Nb with critical temperature $T_{c}=8.5$ K. Magnetization versus temperature (M {\it vs} T) data obtained for fixed magnetic fields above 1 kOe show a superconducting transition which becomes broader as the field is increased. The data are interpreted in terms of the diamagnetic lowest Landau level (LLL) fluctuation theory. The scaling analysis gives values of the superconducting transition temperature $T_{c}(H)$ consistent with $H_{c2}(T)$% . We search for universal 3D LLL behavior by comparing scaling results for Nb and YBaCuO, but obtain no evidence for universality.