Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy

TL;DR

This paper presents the design and testing of superconducting coplanar waveguide resonators that enhance sensitivity in low-temperature pulsed ESR spectroscopy, especially for surface-near spins, with high Q-factors and low power requirements.

Contribution

It introduces a novel superconducting coplanar waveguide resonator design optimized for pulsed ESR, demonstrating improved sensitivity and compatibility with ultra-low temperature measurements.

Findings

Higher sensitivity than conventional waveguide resonators.

High Q-factors achieved with small sample sizes.

Low microwave power compatible with ultra-low temperatures.

Abstract

We discuss the design and implementation of thin film superconducting coplanar waveguide micro- resonators for pulsed ESR experiments. The performance of the resonators with P doped Si epilayer samples is compared to waveguide resonators under equivalent conditions. The high achievable filling factor even for small sized samples and the relatively high Q-factor result in a sensitivity that is superior to that of conventional waveguide resonators, in particular to spins close to the sample surface. The peak microwave power is on the order of a few microwatts, which is compatible with measurements at ultra low temperatures. We also discuss the effect of the nonuniform microwave magnetic field on the Hahn echo power dependence.