Nuclear spin-induced envelope modulation in single NV diamond magnetometry

Abhishek Joshi (Indian Institute of Science Education and Research Bhopal, India)

LinkedIn: Abhishek Joshi

Abstract: Nuclear spins are an ubiquitous probe of the atomic and molecular environment. However, the Nuclear Magnetic Resonance signal does not provide the information related to the hyperfine coupling strength and the nature of the coupled electron. On the other hand, Electron Spin Resonance (ESR), weak magnetic fields from nuclear spins coupled to an electron spin are detected through envelope modulation arising from hyperfine coupling. In this context, the nitrogen-vacancy (NV) center in diamond is a versatile platform for room-temperature ESR studies: its features are optically induced spin polarization at room temperature, coherent manipulation with microwaves, and optical readout via spin-dependent fluorescence.
Prior work has shown that a magnetic field transverse to the NV axis induces electron-nuclear state mixing, thus enabling forbidden microwave transitions that produce envelope modulations in spin-echo experiments. Recently, analogous ^15N-induced modulations were observed in the NV coherence measured in Ramsey experiments performed at low fields (∼ 10 mT). Here, we extend these studies to higher magnetic fields of 45 mT approaching the NV center’s excited-state level anti-crossing (ESLAC), a regime where the current theoretical description based on the perturbation theory fails.
By analyzing the experimental data, we extracted hyperfine parameters, enhancement factors of the nuclear gyromagnetic ratio, and the conditional nuclear Larmor frequencies. Our findings are significant for developing nuclear spin-based quantum sensors and nanoscale quantum sensing in biological systems where NV-nanodiamond probes function in environments with poorly controlled or misaligned magnetic fields.