Large magneto-thermal-switching ratio in superconducting Pb wires

TL;DR

This study demonstrates that pure lead wires exhibit a large magneto-thermal-switching ratio at low temperatures, with the potential for tunable thermal conductivity via magnetic fields and purity levels, advancing low-temperature thermal management technologies.

Contribution

It provides new experimental data on the magneto-thermal-switching ratios of pure Pb wires with different purities, highlighting their potential for low-temperature thermal switching applications.

Findings

5N-Pb shows MTSR exceeding 1000% below 3.6 K under H > 600 Oe.

3N-Pb exhibits a MTSR of 300% at 2.5 K with smaller magnetic-field-induced ppa change.

Higher purity Pb wires have greater potential for large MTSRs in low-temperature regimes.

Abstract

Thermal switching by magnetic fields is one of the important functionalities in thermal management technologies. In low-temperature devices, superconducting states can be used as a magneto-thermal-switching (MTS) component, because carrier thermal conductivity (\k{appa}) is strongly suppressed in superconducting states. Recently, we demonstrated that the MTS ratio (MTSR) of pure Nb reached 650% at a temperature (T) of 2.5 K under a magnetic field (H) of 4.0 kOe [M. Yoshida et al., Appl. Phys. Express 16, 033002 (2023)]. In this study, to enrich knowledge on MTS of superconductors, the MTSRs of pure Pb wires with 5N and 3N purities were investigated by measuring the temperature or magnetic field dependences of \k{appa}. For 5N-Pb, a large MTSR exceeding 1000% was observed below 3.6 K under H > 600 Oe. Although higher MTSRs were expected at lower temperatures under H > 600 Oe, the obtained data under those conditions were accompanied by large errors due to magnetic-field-induced huge \k{appa} at low temperatures. In contrast, the \k{appa} for 3N-Pb were observed to be clearly lower than that for 5N-Pb. Although the magnetic-field-induced change in \k{appa} was small, the MTSR at T = 2.5 K was 300%. These results suggest that Pb is a promising material for low-temperature magneto-thermal switching because of wide-range \k{appa} tunable by magnetic field and the purity.