Demonstration of NV-detected ESR spectroscopy at 115 GHz and 4.2 T

Abstract

High frequency electron spin resonance (ESR) spectroscopy is an invaluable tool for identification and characterization of spin systems. Nanoscale ESR using the nitrogen-vacancy (NV) center has been demonstrated down to the level of a single spin. However, NVdetected ESR has exclusively been studied at low magnetic fields, where spectral overlap prevents clear identification of spectral features. Within this work, we demonstrate NVdetected ESR measurements of single-substitutional nitrogen impurities in diamond at a NV Larmor frequency of 115 GHz and the corresponding magnetic field of 4.2 Tesla. The NV-ESR measurements utilize a double electron-electron resonance sequence and are performed using both ensemble and single NV spin systems. In the single NV experiment, chirp pulses are used to improve the population transfer and for NV-ESR measurements.This work provides the basis for NV-based ESR measurements of external spins at high magnetic fields.The nitrogen-vacancy (NV) center has unique properties that make it an excellent candidate for high sensitivity magnetic sensing. 1-3 The NV center is a two atom defect in the diamond lattice, with the capacity for optical spin-state initialization and readout, long coherence times, and high sensitivity to external magnetic fields. 4-6 NV-detected electron spin resonance (ESR) offers the capability to detect a single or a small number of electron spins 7-12 and to investigate biological molecules at the single molecule level. 13,14 Such an ESR technique with single spin sensitivity potentially eliminates ensembles averaging in heterogeneous and complex systems, and has great promise to directly probe fundamental interactions and biochemical function. In ESR, the measurement of the g-factor is extremely useful for the identification of spin species. However, a featureless "g = 2" signal is often observed, causing spectral overlap with target ESR signals, which may prevent spin identification. [14][15][16][17] Similar to nuclear magnetic resonance spectroscopy, pulsed ESR spectroscopy at higher frequencies (HF) and magnetic fields becomes more powerful for finer spectral resolution, enabling clear spectral separation of systems with similar g values. 18,19 This is advantageous in the investigation of complex and heterogeneous spin systems. 20,21 A high frequency of Larmor precession is also less sensitive to motional narrowing, enabling the ESR investigation of structures for molecules in motion. 22,23 In addition, a high Larmor frequency provides greater spin polarization:improving sensitivity 18,19 and providing control of spin dynamics. 24,25 On the other hand, pulsed HF ESR often has the disadvantage of long pulse times due to low HF microwave power. Moreover, the low microwave power limits the excitation bandwidth, and consequently the sensitivity of pulse ESR measurements. NV-detected ESR (indicated as NV-ESR) at a high frequency will enable ESR with drastically improved sensitivity and spectral resolution. However, only a few investigations of NV centers have been...

Electron-electron double resonance detected NMR spectroscopy using ensemble NV centers at 230 GHz and 8.3 Tesla

“…Additional details of the HF-ESR/ODMR spectrometer have been described previously. 22,23,33,34 For this study a 2.0 × 2.0 × 0.3 mm 3 size, (111)-cut high pressure, high temperature type Ib diamond from Sumitomo Electric Industries was utilized. The diamond had previously been subjected to high fluence electron irradiation and annealing to increase the concentration of NV centers.…”

“…However, there have only been a handful of studies on NV-based sensing at high magnetic fields due to technological challenges combining the NV ODMR system with a high magnetic field ESR system. [22][23][24][25] In this paper, we discuss the implementation of NV-detected NMR at a high magnetic field.…”

“…Therefore, the described NV-detected NMR technique will be advantageous for the development of NV-detected NMR at higher fields and frequencies where the microwave power and pulsed ESR capabilities are often limited. 23,31,32…”

High-Field Magnetometry with Hyperpolarized Nuclear Spins

“…Instead, for applications in NMR, high fields are naturally advantageous because the chemical shift dispersion is larger, and analyte nuclei carry higher polarization [13]. The challenge of accessing this regime arises from the rapidly scaling electronic magnetogyric ratio 𝛾 𝑒 , that makes electronic control difficult at high fields [14,15]. Simultaneously, precise field alignment [16] is required to obtain viable NV spin-readout contrast [17].…”

“…While our experiments were carried out at 7 T, the slow scaling 13 C magnetogyric ratio makes sensing viable even for fields 24 T. This greatly expands the field range for spin sensors, where the operating field is predominantly <0.3 T (notable exceptions are Refs. [13,15], but require complex instrumentation).…”