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Engineering Dark Spin-Free Diamond Interfaces
Preprint   Open access

Engineering Dark Spin-Free Diamond Interfaces

Xiaofei Yu, Evan J Villafranca, Stella Wang, Jessica C Jones, Mouzhe Xie, Jonah Nagura, Ignacio Chi-Durán, Nazar Delegan, Alex B. F Martinson, Michael E Flatté, …
ArXiV.org
Cornell University
04/11/2025
DOI: 10.48550/arxiv.2504.08883
url
https://doi.org/10.48550/arxiv.2504.08883View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

Nitrogen-vacancy (NV) centers in diamond are extensively utilized as quantum sensors for imaging fields at the nanoscale. The ultra-high sensitivity of NV magnetometers has enabled the detection and spectroscopy of individual electron spins, with potentially far-reaching applications in condensed matter physics, spintronics, and molecular biology. However, the surfaces of these diamond sensors naturally contain electron spins, which create a background signal that can be hard to differentiate from the signal of the target spins. In this study, we develop a surface modification approach that eliminates the unwanted signal of these so-called dark electron spins. Our surface passivation technique, based on coating diamond surfaces with a thin titanium oxide (TiO2) layer, reduces the dark spin density. The observed reduction in dark spin density aligns with our findings on the electronic structure of the diamond-TiO2 interface. The reduction, from a typical value of 2,000~μm−2 to a value below that set by the detection limit of our NV sensors (200~μm−2), results in a two-fold increase in spin echo coherence time of near surface NV centers. Furthermore, we derive a comprehensive spin model that connects dark spin depolarization with NV coherence, providing additional insights into the mechanisms behind the observed spin dynamics. Our findings are directly transferable to other quantum platforms, including nanoscale solid state qubits and superconducting qubits.
Physics - Mesoscale and Nanoscale Physics Physics - Quantum Physics

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