Joule heating and high frequency nonlinear effects in the surface impedance of high Tc superconductors

TL;DR

This study investigates the nonlinear surface impedance of high Tc superconducting thin films at microwave frequencies, revealing that observed resistance increases are primarily due to local heating effects.

Contribution

It introduces a dielectric resonator method with precise temperature measurement to distinguish between intrinsic nonlinearities and heating effects in superconducting films.

Findings

Surface resistance increase is caused by local heating.

Dielectric resonator enables precise temperature control during measurements.

Nonlinear effects are dominated by Joule heating rather than intrinsic properties.

Abstract

Using the dielectric resonator method, we have investigated nonlinearities in the surface impedance Zs = Rs + jXs of YBa2Cu3O7 thin films at 10 GHz as function of the incident microwave power level and temperature. The use of a rutile dielectric resonator allows us to measure the precise temperature of the films. We conclusively show that the usually observed increase of the surface resistance of YBa2Cu3O7 thin film as function of microwave power is due to local heating.