Quantum paraelectricity probed by superconducting resonators

TL;DR

This study uses superconducting resonators to investigate the quantum paraelectric behavior of SrTiO3 at low temperatures and high frequencies, revealing dielectric properties and fatigue effects related to oxygen vacancies.

Contribution

It introduces a novel application of superconducting CPW resonators to quantitatively analyze SrTiO3's dielectric properties near a ferroelectric transition.

Findings

SrTiO3 exhibits quantum paraelectricity at low temperatures.

Dielectric permittivity is tunable with external bias and RF power.

Oxygen vacancies contribute to fatigue and reduced tunability.

Abstract

Superconducting coplanar waveguide (CPW), resonators are powerful and versatile tools used in areas ranging from radiation detection to circuit quantum electrodynamics. Their potential for low intrinsic losses makes them attractive as sensitive probes of electronic properties of bulk materials and thin films. Here we use superconducting MoRe CPW resonators, to investigate the high-frequency (up to 0.3 GHz) and low temperature (down to 3.5 K) permittivity of SrTiO3, a non-linear dielectric on the verge of a ferroelectric transition (quantum paraelectricity). We perform a quantitative analysis of its dielectric properties as a function of external dc bias (up to +-15V), rf power and mode number and discuss our results within the framework of the most recent theoretical models. We also discuss the origin of a fatigue effect that reduces the tunability of the dielectric constant of SrTiO3, which we relate to the presence of oxygen vacancies.