Search for: All records

Abstract Understanding the behavior of confined water at liquid–solid interfaces is central to numerous physical, chemical, and biological processes, yet remains experimentally challenging. Here, shallow nitrogen‐vacancy (NV) centers in diamond serve as sensors to investigate the nanoscale dynamics of interfacial water confined between the diamond surface and an overlying fluorinated oil droplet. With the help of nuclear magnetic resonance (NMR) protocols selectively sensitive to¹H and¹⁹F, NVs are used to probe water and oil near the interface under ambient conditions. Comparing opposite sides of a doubly‐implanted diamond membrane — one exposed to oil, the other not — a slow, multi‐day process is uncovered in which the interfacial water layer is gradually depleted. This desorption appears to be driven by sustained interactions with the fluorinated oil and is supported by molecular dynamics simulations and surface‐sensitive X‐ray spectroscopies. These findings provide molecular‐level insight into long‐timescale hydration dynamics and underscore the power of NV‐NMR for probing liquid–solid heterointerfaces with chemical specificity. 

Abstract Extending the coherence lifetime of a qubit is central to the implementation and deployment of quantum technologies, particularly in the solid state where various noise sources intrinsic to the material host play a limiting role. This study examines theoretically the coherent spin dynamics of a hetero‐spin system formed by a spin featuring a non‐zero crystal field and in proximity to a paramagnetic center . An analysis of the energy level structure of the dyad shows this system exhibits apair of levels separated by a magnetic‐field‐insensitive energy gap, which can be exploited to create long‐lived zero‐quantum coherences. It is found that these coherences are selectively sensitive to “local”—as opposed to “global”—magnetic field fluctuations, suggesting these spin dyads can serve as a nanoscale gradiometer for precision magnetometry. On the other hand, the distinct response of either spin species to electric or thermal stimuli allows one to implement alternative sensing protocols for magnetic‐noise‐free electrometry and thermometry. 

Color centers in hexagonal boron nitride (hBN) are presently attracting broad interest as a novel platform for nanoscale sensing and quantum information processing. Unfortunately, their atomic structures remain largely elusive and only a small percentage of the emitters studied thus far have the properties required to serve as optically addressable spin qubits. Here, we use confocal fluorescence microscopy at variable temperatures to study a new class of point defects produced via cerium ion implantation in thin hBN flakes. We find that, to a significant fraction, emitters show bright room-temperature emission, and good optical stability suggesting the formation of Ce-based point defects. Using density functional theory (DFT) we calculate the emission properties of candidate emitters, and single out the CeV_Bcenter—formed by an interlayer Ce atom adjacent to a boron vacancy—as one possible microscopic model. Our results suggest an intriguing route to defect engineering that simultaneously exploits the singular properties of rare-earth ions and the versatility of two-dimensional material hosts. 

Disorder and many body interactions are known to impact transport and thermalization in competing ways, with the dominance of one or the other giving rise to fundamentally different dynamical phases. Here we investigate the spin diffusion dynamics of 13 C in diamond, which we dynamically polarize at room temperature via optical spin pumping of engineered color centers. We focus on low-abundance, strongly hyperfine-coupled nuclei, whose role in the polarization transport we expose through the integrated impact of variable radio-frequency excitation on the observable bulk 13 C magnetic resonance signal. Unexpectedly, we find good thermal contact throughout the nuclear spin bath, virtually independent of the hyperfine coupling strength, which we attribute to effective carbon-carbon interactions mediated by the electronic spin ensemble. In particular, observations across the full range of hyperfine couplings indicate the nuclear spin diffusion constant takes values up to two orders of magnitude greater than that expected from homo-nuclear spin couplings.