Spin defects in aqueous environments and confined geometries*

Nano nuclear magnetic resonance (nano-NMR) spectroscopy aims at applying NMR techniques to nanoscale samples, and eventually at enabling high-resolution imaging of single molecules. The nitrogen-vacancy (NV) center-based spectrometer is a promising platform for nano-NMR: the defect characteristic decoherence time (T2) can be used, for example, to observe the time evolution of proton spins from simple molecules located in proximity of a diamond surface. In this work, we analyzed the magnetic field induced by protons of water in confined geometries and how this affects the coherence times of spin defects in two-dimensional materials, including graphene and h-BN. We considered graphene and hexagonal boron nitride (hBN) layers as test systems and generated a structural model of the layer/water interface by performing classical molecular dynamics (MD) simulations using the LAMMPS code. We then used the MD trajectories to generate spin bath configurations and compute hyperfine interactions using the PyCCE code [1]. An NV-like spin defect in graphene and a negatively charged boron-vacancy in hBN were considered. In this talk, we will discuss how both the parallel and perpendicular components of the magnetic noise induced by protons affects the lifetime of the spin qubit. 

[1] Onizhuk, M. et al. Adv. Theory Simul. 2021