Microwave probing of bulk dielectrics using superconducting coplanar resonators in distant-flip-chip geometry

TL;DR

This paper introduces a novel microwave technique using superconducting coplanar resonators in distant-flip-chip geometry to measure the dielectric properties of bulk insulators at cryogenic temperatures and GHz frequencies.

Contribution

The study presents a new method for dielectric characterization of bulk materials at GHz frequencies using superconducting resonators in a distant-flip-chip setup.

Findings

Successfully measured dielectric properties of MgO, LaAlO3, and TiO2.

Operated effectively at temperatures between 1.4 K and 7 K.

Achieved probing frequencies up to 20 GHz.

Abstract

Dielectric measurements on insulating materials at cryogenic temperatures can be challenging, depending on the frequency and temperature ranges of interest. We present a technique to study the dielectric properties of bulk dielectrics at GHz frequencies. A superconducting coplanar Nb resonator is deposited directly on the material of interest, and this resonator is then probed in distant-flip-chip geometry with a microwave feedline on a separate chip. Evaluating several harmonics of the resonator gives access to various probing frequencies, in the present studies up to 20 GHz. We demonstrate the technique on three different materials (MgO, LaAlO3, and TiO2), at temperatures between 1.4 K and 7 K.