Nanoscale zero-field electron spin resonance spectroscopy

Abstract

Electron spin resonance (ESR) spectroscopy has broad applications in physics, chemistry, and biology. As a complementary tool, zero-field ESR (ZF-ESR) spectroscopy has been proposed for decades and shown its own benefits for investigating the electron fine and hyperfine interaction. However, the ZF-ESR method has been rarely used due to the low sensitivity and the requirement of much larger samples than conventional ESR. In this work, we present a method for deploying ZF-ESR spectroscopy at the nanoscale by using a highly sensitive quantum sensor, the nitrogen vacancy center in diamond. We also measure the nanoscale ZF-ESR spectrum of a few P1 centers in diamond, and show that the hyperfine coupling constant can be directly extracted from the spectrum. This method opens the door to practical applications of ZF-ESR spectroscopy, such as investigation of the structure and polarity information in spin-modified organic and biological systems.

Zero-Field Magnetometry Based on Nitrogen-Vacancy Ensembles in Diamond

“…Negatively charged nitrogen-vacancy (NV) centers in diamond have garnered wide interest as magnetometers [1][2][3][4][5][6], with diverse applications ranging from electron spin resonance (ESR) and biophysics to materials science [7][8][9][10][11][12][13]. However, typical operation of an NV magnetometer requires an applied bias magnetic field to nonambiguously resolve magnetically sensitive features in the level structure.…”

Kilohertz electron paramagnetic resonance spectroscopy of single nitrogen centers at zero magnetic field

“…Such a narrowed ST 0 spectrum is challenging to observe by the previous microwave power-sweeping method ( 12 ), as it requires extreme power stability of the entire microwave circuits. The commonly used double electron-electron resonance (DEER) method ( 5 – 10 ) is also not suitable, because the interrogation time is limited by the coherence time T 2 of the NV center.…”

“…Inspired by the correlation spectroscopy of nuclear spins ( 16 ), we develop a modified correlation detection protocol for zero-field EPR spectroscopy. Then, the sensor’s lifetime can be increased to the spin-locking relaxation time T 1ρ , which is usually much longer than T 2 for shallow NV centers ( 12 , 29 ).…”

“…If successfully generalizing to external paramagnetic targets, this technique will benefit many EPR studies with substantially improved precision. For example, zero-field EPR spectroscopy is a powerful tool to unambiguously extract the hyperfine constants (12), which can reflect the local polarity profiles (14). By improving spectral resolution, more detailed microenvironment information can be explored.…”

“…Fortunately, the NV center is a good magnetic sensor at zero magnetic field (28). In a previous study (12), we have found that the NV center is a promising sensor for zero-field EPR without loss of sensitivity, because the statistical fluctuations of the spin polarization, which do not depend on the magnetic field, dominate in its nanoscale detection volumes rather than thermal polarization.…”