Low-temperature magnetic-field-driven thermal oscillator based on metal-superconductor joint

Thermal control is one of the important technologies for fundamental science and thermal management. Among them, thermal oscillators have been in demands in the field of materials science and device application. In general, flexible frequency, amplitude, and waveform are needed for useful thermal oscillator, and the stability of the average temperature is also highly required. However, thermal oscillators based on an AC-current-driven heater require complicated control of input power to achieve the above-mentioned flexibility and stability of the outputs. Here, we demonstrate that magnetically-driven thermal oscillators fabricated using a metal-superconductor (Cu-Pb) joint achieve those requirements easily by tuning the applied magnetic field ( H ). A DC-current-driven heater is attached on the metal (Cu) side, and the superconductor (Pb) edge is attached to thermal bath. We use a sharp and huge change in thermal conductivity at the superconducting transition of the Pb wire to generate thermal oscillation at the Cu-wire side. A sine-shaped thermal oscillation with an amplitude of 180 mK and a frequency of 0.17 Hz is observed with highly stable average temperature. Furthermore, a larger amplitude is achieved in a square-shaped oscillation with a larger H amplitude. Our thermal oscillator with temperature stability, large amplitude, and relatively high frequency will work as a flexible AC heat source at cryogenic temperatures.