Microwave heating-induced DC magnetic flux penetration in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ superconducting thin films

TL;DR

This study visualizes how microwave heating influences magnetic flux penetration in YBa2Cu3O7-delta superconducting thin films, revealing that increased temperature from microwave power facilitates flux entry under certain magnetic conditions.

Contribution

It demonstrates that microwave-induced flux penetration in superconducting films is primarily due to local heating effects, providing insight into microwave-superconductor interactions.

Findings

No flux penetration occurs with microwave magnetic field alone at high power.

Flux penetration progresses with increasing microwave magnetic field when a static magnetic field is present.

Flux entry is caused by temperature increase from microwave heating, not direct microwave magnetic field effects.

Abstract

The magneto-optical imaging technique is used to visualize the penetration of the magnetic induction in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films during surface resistance measurements. The in-situ surface resistance measurements were performed at 7 GHz using the dielectric resonator method. When only the microwave magnetic field $H_{rf}$ is applied to the superconductor, no $H_{rf}$-induced vortex penetration is observed, even at high rf power. In contrast, in the presence of a constant magnetic field superimposed on $H_{rf}$ we observe a progression of the flux front as $H_{rf}$ is increased. A local thermometry method based on the measurement of the resonant frequency of the dielectric resonator placed on the YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin film shows that the $H_{rf}$--induced flux penetration is due to the increase of the film temperature.