Power-law scaling of correlations in statistically polarised nano-NMR

TL;DR

This paper demonstrates that in nano-NMR, nuclear spin correlations decay following a power-law rather than exponentially, enabling sharper spectral lines and potentially improving resolution in nano-scale magnetic resonance measurements.

Contribution

The study provides experimental evidence of power-law decay of correlations in nano-NMR, challenging the traditional exponential decay assumption and suggesting enhanced spectral resolution possibilities.

Findings

Power-law decay of correlations observed in nano-NMR.

Spectral lines are sharper due to reduced diffusion broadening.

Experimental evidence from three different setups supports the findings.

Abstract

Diffusion noise is a major source of spectral line broadening in liquid state nano-scale nuclear magnetic resonance with shallow nitrogen-vacancy centres, whose main consequence is a limited spectral resolution. This limitation arises by virtue of the widely accepted assumption that nuclear spin signal correlations decay exponentially in nano-NMR. However, a more accurate analysis of diffusion shows that correlations survive for a longer time due to a power-law scaling, yielding the possibility for improved resolution and altering our understanding of diffusion at the nano-scale. Nevertheless, such behaviour remains to be demonstrated in experiments. Using three different experimental setups and disparate measurement techniques, we present overwhelming evidence of power-law decay of correlations. These result in sharp-peaked spectral lines, for which diffusion broadening need not be a limitation to resolution.