Dynamical decoupling of interacting dipolar spin ensembles

TL;DR

This paper shows that specific pulse sequences can effectively reduce dipolar interactions in solid-state electron spin systems, improving coherence times even with imperfect pulses, through simulations and experiments.

Contribution

It introduces a simulation approach that models dipolar spin interactions under pulse sequences without requiring complex hardware, and demonstrates the effectiveness of XYXY sequences over CPMG in ESR.

Findings

CPMG and XYXY sequences reduce dipolar interactions in ESR.

Small pulse imperfections (<10%) still allow effective refocusing of interactions.

XYXY sequences cause less inflation of echo decay times compared to CPMG.

Abstract

We demonstrate that CPMG and XYXY decoupling sequences with non-ideal $\pi$ pulses can reduce dipolar interactions between spins of the same species in solids. Our simulations of pulsed electron spin resonance (ESR) experiments show that $\pi$ rotations with small ($<$~10\%) imperfections refocus instantaneous diffusion. Here, the intractable N-body problem of interacting dipoles is approximated by the average evolution of a single spin in a changing mean field. These calculations agree well with experiments and do not require powerful hardware. Our results add to past attempts to explain similar phenomena in solid state nuclear magnetic resonance (NMR). Although the fundamental physics of NMR are similar to ESR, the larger linewidths in ESR and stronger dipolar interactions between electron spins compared to nuclear spins preclude drawing conclusions from NMR studies alone. For bulk spins, we also find that using XYXY results in less inflation of the deduced echo decay times as compared to decays obtained with CPMG.