Nanoscale spin detection of copper ions using double electron-electron resonance at room temperature

TL;DR

This paper demonstrates nanoscale detection of copper ions' spins at room temperature using double electron-electron resonance with diamond-based sensors, revealing narrow resonances and hyperfine interactions.

Contribution

It introduces a method for detecting copper ion spins at the nanoscale with high sensitivity at room temperature using DEER in diamond.

Findings

Narrow EPR resonances with linewidths of 2-3 MHz.

Observation of coherent Rabi oscillations and hyperfine splitting.

Sensing volume of approximately (250 nm)^3.

Abstract

We report the nanoscale spin detection and electron paramagnetic resonance (EPR) spectrum of copper (Cu$^{2+}$) ions via double electron-electron resonance with single spins in diamond at room temperature and low magnetic fields. We measure unexpectedly narrow EPR resonances with linewidths $\sim 2-3$ MHz from copper-chloride molecules dissolved in poly-lysine. We also observe coherent Rabi oscillations and hyperfine splitting from single Cu$^{2+}$ ions, which could be used for dynamic nuclear spin polarization and higher sensitivity of spin detection. We interpret and analyze these observations using both spin hamiltonian modeling of the copper-chloride molecules and numerical simulations of the predicted DEER response, and obtain a sensing volume $\sim (250 \text{nm})^3$. This work will open the door for copper-labeled EPR measurements under ambient conditions in bio-molecules and nano-materials.