Superconducting Magnetization above the Irreversibility Line in Tl2Ba2CuO6

TL;DR

This study uses torque magnetometry to measure magnetization in Tl2Ba2CuO6, revealing persistent superconducting diamagnetism above the irreversibility line, especially in overdoped samples, challenging simple vortex liquid models.

Contribution

It provides new experimental evidence of superconducting order above the irreversibility line in Tl2Ba2CuO6, highlighting a linear diamagnetic response in overdoped crystals.

Findings

Magnetization above the irreversibility line deviates from simple vortex liquid behavior.

Overdoped crystals show a linear diamagnetic response persisting above Tc.

Superconducting order remains detectable well above the irreversibility line.

Abstract

Piezolever torque magnetometry has been used to measure the magnetization of superconducting Tl2Ba2CuO6. Three crystals with different levels of oxygen overdoping were investigated in magnetic fields up to 10 Tesla. In all cases, the magnetization above the irreversibility line was found to depart from the behaviour M ~ ln(Hc2/H) of a simple London-like vortex liquid. In particular, for a strongly overdoped (Tc = 15K) crystal, the remnant superconducting order above the irreversibility line is characterized by a linear diamagnetic response (M ~ H) that persists well above Tc and also up to the highest field employed.