Electron Paramagnetic Resonance Spectroscopy of Er$^{3+}$:Y$_2$SiO$_5$ Using Josephson Bifurcation Amplifier: Observation of Hyperfine and Quadrupole Structures

TL;DR

This study demonstrates high-sensitivity electron paramagnetic resonance spectroscopy of Er$^{3+}$:Y$_2$SiO$_5$ using a Josephson bifurcation amplifier, revealing hyperfine and quadrupole structures with improved detection capabilities.

Contribution

It introduces a novel application of a Josephson bifurcation amplifier for ESR spectroscopy, achieving enhanced sensitivity and detailed hyperfine and quadrupole structure observation.

Findings

Spectra match well with simulated energy levels including hyperfine and quadrupole interactions.

Achieved a measurement sensitivity of approximately 1.5×10^4 electron spins in 1 second.

Sensitivity is two orders of magnitude better than previous dc-SQUID based methods.

Abstract

We performed magnetic field and frequency tunable electron paramagnetic resonance spectroscopy of an Er$^{3+}$ doped Y$_2$SiO$_5$ crystal by observing the change in flux induced on a direct current-superconducting quantum interference device (dc-SQUID) loop of a tunable Josephson bifurcation amplifer. The observed spectra show multiple transitions which agree well with the simulated energy levels, taking into account the hyperfine and quadrupole interactions of $^{167}$Er. The sensing volume is about 0.15 pl, and our inferred measurement sensitivity (limited by external flux noise) is approximately $1.5\times10^4$ electron spins for a 1 s measurement. The sensitivity value is two orders of magnitude better than similar schemes using dc-SQUID switching readout.