Nonlinear Induction Detection of Electron Spin Resonance

TL;DR

This paper introduces a nonlinear superconducting resonator method for electron spin resonance detection, significantly enhancing sensitivity by exploiting thermal nonlinearities in a YBCO microbridge.

Contribution

It presents a novel nonlinear detection technique for ESR using a superconducting resonator with a microbridge, improving responsivity near the instability threshold.

Findings

Responsivity increased by about 100 times near the nonlinear threshold.

Preliminary experimental results support the theoretical model.

Potential for improved ESR detection sensitivity over conventional methods.

Abstract

We present a new approach to the induction detection of electron spin resonance (ESR) signals exploiting the nonlinear properties of a superconducting resonator. Our experiments employ a yttrium barium copper oxide (YBCO) superconducting stripline microwave (MW) resonator integrated with a microbridge. A strong nonlinear response of the resonator is thermally activated in the microbridge when exceeding a threshold in the injected MW power. The responsivity factor characterizing the ESR-induced change in the system's output signal is about 100 times larger when operating the resonator near the instability threshold, compared to the value obtained in the linear regime of operation. Preliminary experimental results, together with a theoretical model of this phenomenon are presented. Under appropriate conditions nonlinear induction detection of ESR can potentially improve upon the current capabilities of conventional linear induction detection ESR.