# Understanding the Linewidth of the ESR Spectrum Detected by a Single NV Center in Diamond

## TL;DR

This study investigates the linewidth of NV-detected ESR in diamond, revealing that spectral resolution is limited by inhomogeneous broadening and demonstrating linewidths as narrow as 0.3 MHz, advancing nanoscale ESR understanding.

## Contribution

The paper provides a detailed analysis of NV-ESR linewidths and identifies the primary limiting factors, offering insights for improving nanoscale ESR sensitivity.

## Key findings

- NV-ESR linewidth can be as narrow as 0.3 MHz
- Spectral resolution is limited by inhomogeneous broadening
- Inhomogeneous broadening significantly affects ESR spectral resolution

## Abstract

Spectral analysis of electron spin resonance (ESR) is a powerful technique for various investigations including characterization of spin systems, measurements of spin concentration, and probing spin dynamics. The nitrogen-vacancy (NV) center in diamond is a promising magnetic sensor enabling improvement of ESR sensitivity to the level of a single spin. Therefore, understanding the nature of NV-detected ESR (NV-ESR) spectrum is critical for applications to nanoscale ESR. Within this work we investigate the linewidth of NV-ESR from single substitutional nitrogen centers (called P1 centers). NV-ESR is detected by a double electron-electron resonance (DEER) technique. By studying the dependence of the DEER excitation bandwidth on NV-ESR linewidth, we find that the spectral resolution is improved significantly and eventually limited by inhomogeneous broadening of the detected P1 ESR. Moreover, we show that the NV-ESR linewidth can be as narrow as 0.3 MHz.