Coherently coupling distinct spin ensembles through a high-$T_c$ superconducting resonator

TL;DR

This paper demonstrates the coherent coupling of multiple spin ensembles via a high-$T_c$ superconducting resonator, achieving strong coupling and simultaneous interaction of three ensembles distinguished by chemical and magnetic inhomogeneities.

Contribution

It introduces a method to coherently couple multiple, physically distinguishable spin ensembles using a high-$T_c$ superconducting resonator, with experimental and theoretical validation.

Findings

Achieved exceptionally strong coupling between spin ensembles and the resonator.

Demonstrated simultaneous coupling of up to three distinguishable spin ensembles.

Observed multiple anticrossings indicating coherent mixing of modes.

Abstract

The problem of coupling multiple spin ensembles through cavity photons is revisited by using PyBTM organic radicals and a high-$T_c$ superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the $g$ factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.