Echo trains in pulsed electron spin resonance of a strongly coupled spin ensemble

TL;DR

This paper reports the discovery of a new dynamical phenomenon in electron spin resonance involving echo trains caused by strong coupling between phosphorus donors and a superconducting resonator, explained through a spin model.

Contribution

It introduces the observation of periodic echo trains in ESR experiments with strongly coupled spin ensembles, supported by theoretical modeling and numerical simulations.

Findings

Observation of self-stimulated echo trains in ESR.

Explanation using Bloch sphere and Tavis-Cummings model.

Demonstration of strong coupling effects in spin-resonator systems.

Abstract

We report on a novel dynamical phenomenon in electron spin resonance experiments of phosphorus donors. When strongly coupling the paramagnetic ensemble to a superconducting lumped element resonator, the coherent exchange between these two subsystems leads to a train of periodic, self-stimulated echos after a conventional Hahn echo pulse sequence. The presence of these multi-echo signatures is explained using a simple model based on spins rotating on the Bloch sphere, backed up by numerical calculations using the inhomogeneous Tavis-Cummings Hamiltonian.