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arXiv:2103.12807

Magnetic field-assisted spectral decomposition and imaging of charge states of NV centers in diamond

Tanmoy Chakraborty, R. Bhattacharya, V. S. Anjusha, M. Nesladek, Dieter Suter, T. S. Mahesh

Published Mar 23, 2021• 0 citations
arXivHTMLPDF

Abstract

With the advent of quantum technology, nitrogen vacancy ($NV$) centers in diamond turn out to be a frontier which provides an efficient platform for quantum computation, communication and sensing applications. Due to the coupled spin-charge dynamics of the $NV$ system, knowledge about $NV$ charge state dynamics can help to formulate efficient spin control sequences strategically. Through this paper we report two spectroscopy-based deconvolution methods to create charge state mapping images of ensembles of $NV$ centers in diamond. First, relying on the fact that an off axis external magnetic field mixes the electronic spins and selectively modifies the photoluminescence (PL) of $NV^-$, we perform decomposition of the optical spectrum for an ensemble of $NV$s and extract the spectra for $NV^-$ and $NV^0$ states. Next, we introduce an optical filter based decomposition protocol and perform PL imaging for $NV^-$ and $NV^0$. Earlier obtained spectra for $NV^-$ and $NV^0$ states are used to calculate their transmissivities through a long pass optical filter. These results help us to determine the spatial distribution of the $NV$ charge states in a diamond sample.

DOI
10.48550/arxiv.2103.12807

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With the advent of quantum technology, nitrogen vacancy (NVNVNV) centers in diamond turn out to be a frontier which provides an efficient platform for quantum computation, communication and sensing applications. Due to the coupled spin-charge dynamics of the NVNVNV system, knowledge about NVNVNV charge state dynamics can help to formulate efficient spin control sequences strategically. Through this paper we report two spectroscopy-based deconvolution methods to create charge state mapping images of ensembles of NVNVNV centers in diamond. First, relying on the fact that an off axis external magnetic field mixes the electronic spins and selectively modifies the photoluminescence (PL) of NV−NV^-NV−, we perform decomposition of the optical spectrum for an ensemble of NVNVNVs and extract the spectra for NV−NV^-NV− and NV0NV^0NV0 states. Next, we introduce an optical filter based decomposition protocol and perform PL imaging for NV−NV^-NV− and NV0NV^0NV0. Earlier obtained spectra for NV−NV^-NV− and NV0NV^0NV0 states are used to calculate their transmissivities through a long pass optical filter. These results help us to determine the spatial distribution of the NVNVNV charge states in a diamond sample.
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Abstract Transverse-magnetic-field-induced spin mixing in nitrogen-vacancy (NV) centers hybridizes the |0⟩ and | ± 1⟩ manifolds, degrading optical spin polarization and spin-dependent fluorescence and thereby limiting optically detected magnetic resonance (ODMR) contrast and quantum-sensor fidelity. While recent work has clarified key elements of NV photophysics, how spin mixing evolves with temperature under device-relevant operating conditions─and how it intertwines with charge-state dynamics─remains insufficiently quantified. Here we perform systematic magnetic-field-temperature (B-T) mapping of transverse-field-induced photoluminescence (PL) quenching in an ensemble of NV centers. By spectrally resolving the NV– and NV0 zero-phonon-line emission, we disentangle spin-mixing-driven contrast loss within NV– from correlated changes in charge-state-resolved fluorescence. We introduce an operational critical field Bc extracted from the PL-contrast line shape, which provides a compact, reproducible figure-of-merit for transverse-field robustness and enables straightforward comparison across temperatures and field geometries. The measured temperature dependence of Bc is captured by a concise model incorporating phonon-mediated excited-state orbital dynamics, establishing a predictive framework for optimizing operating conditions and benchmarking ensemble NV sensing platforms.
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In recent years, nitrogen-vacancy (NV) color centers in diamond have become excellent solid-state quantum sensors due to their electronic spin properties. Especially for their easy optical initialization and detection, together with their very large spin coherence at room temperature. Many studies have reported their use for sensing temperature, strain, electric fields, and mainly magnetic fields. Here, we show how to build a two-dimensional map of the electronic spin coherence of an ensemble of NV centers in ultra-pure diamond, using an optical imaging protocol combined with microwave pulses relying simply on a regular CCD camera.
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Nitrogen vacancy (NV) centers in diamond are at the heart of many emerging quantum technologies, all of which require control over the NV charge state. Hence, methods for quantification of the relative photoluminescence intensities of the NV0 and NV− charge states, i.e., a charge state ratio, are vital. Several approaches to quantify NV charge state ratios have been reported but are either limited to bulk-like NV diamond samples or yield qualitative results. We propose an NV charge state quantification protocol based on the determination of sample- and experimental setup-specific NV0 and NV− reference spectra. The approach employs blue (400–470 nm) and green (480–570 nm) excitation to infer pure NV0 and NV− spectra, which are then used to quantify NV charge state ratios in subsequent experiments via least squares fitting. We test our dual excitation protocol (DEP) for a bulk diamond NV sample and 20 and 100 nm nanodiamond particles and compare results with those obtained via other commonly used techniques such as zero-phonon line fitting and non-negative matrix factorization. We find that DEP can be employed across different samples and experimental setups and yields consistent and quantitative results for NV charge state ratios that are in agreement with our understanding of NV photophysics. By providing robust NV charge state quantification across sample types and measurement platforms, DEP will support the development of NV-based quantum technologies.