Free induction decay of single spins in diamond

TL;DR

This study combines theory and experiments to analyze the free induction decay of a single electron spin in diamond, revealing how magnetic fields extend coherence times and identifying nuclear spins responsible for decoherence.

Contribution

It provides a systematic experimental and theoretical analysis of FID in NV centers, showing magnetic field enhancement of coherence and identifying key nuclear spins affecting decoherence.

Findings

Coherence time increases by a factor of √(5/2) at high magnetic fields.

Enhancement of coherence is independent of nuclear spin impurity concentration.

Identification of specific nuclear spins responsible for decoherence dynamics.

Abstract

We study both theoretically and experimentally the free induction decay (FID) of the electron spin associated with a single nitrogen-vacancy defect in high purity diamond, where the main source of decoherence is the hyperfine interaction with a bath of $^{13}$C nuclear spins. In particular, we report a systematic study of the FID signal as a function of the strength of a magnetic field oriented along the symmetry axis of the defect. On average, an increment of the coherence time by a factor of $\sqrt{5/2}$ is observed at high magnetic field in diamond samples with a natural abundance of $^{13}$C nuclear spins, in agreement with numerical simulations and theoretical studies. Further theoretical analysis shows that this enhancement is independent of the concentration of nuclear spin impurities. By dividing the nuclear spin bath into shells and cones, we theoretically identify which nuclear spins are responsible for the observed dynamics.