P1 Center Electron Spin Clusters Are Prevalent in Type Ib Diamonds

Bussandri, Santiago; Shimon, Daphna; Equbal, Asif; Ren, Yuhang; Takahashi, Susumu; Ramanathan, Chandrasekhar; Han, Songi

doi:10.1021/jacs.3c06705

Cited by 9 publications

(8 citation statements)

References 71 publications

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“…Additionally, our work establishes the high-field dual EPR/DNP approach as an informative probe for the detection of strongly interacting, clustered paramagnetic centers beyond what is possible with other methods. Similar conclusions were reached by the group of Han and co-workers …”

Section: Introductionsupporting

confidence: 89%

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Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Nir-Arad,

Shlomi,

Manukovsky

et al. 2023

J. Am. Chem. Soc.

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Diamonds have been shown to be an excellent platform for quantum computing and quantum sensing applications. These applications are enabled by the presence of defects in the lattice, which are also known as color centers. The most common nitrogen-based defect in synthetic diamonds is the paramagnetic nitrogen substitution (P1) center. While the majority of quantum applications rely on nitrogen-vacancy (NV) centers, the properties of the latter are heavily influenced by the presence and the spatial distribution of the P1 centers. Hence, understanding the spatial distribution and mutual interactions of P1 centers is crucial for the successful development of diamond-based quantum devices. Unlike NV centers, P1 centers do not have a spin-dependent optical signature, and their spin-related properties, therefore, have to be detected and characterized using magnetic resonance methods. We show that using high-field (6.9 and 13.8 T) pulsed electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP) experiments, we can distinguish and quantify three distinct populations of P1 centers: isolated P1 centers, weakly interacting ones, and exchange-coupled ones that are clustered together. While such clustering was suggested before, these clusters were never detected directly and unambiguously. Moreover, by using electron−electron double resonance (ELDOR) pump−probe experiments, we demonstrate that the latter clustered population does not exist in isolation but coexists with the more weakly interacting P1 centers throughout the diamond lattice. Its presence thus strongly affects the quantum properties of the diamond. We also show that the existence of this population can explain recent hyperpolarization results in type Ib high-pressure, high-temperature (HPHT) diamonds. We propose a combination of high-field pulsed EPR, ELDOR, and DNP as a tool for probing the aggregation state and interactions among different populations of nitrogen substitution centers.

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Section: Introductionsupporting

confidence: 89%

“…The latter requires ≫1 GHz exchange coupling constant to simulate the results and was assigned to P1 centers pairs . A similar conclusion on the presence of the exchange-coupled clusters was reached based on the increase in the Rabi nuation frequency for the signals in between the resolved P1 centers in microdiamond powder samples …”

Section: Resultssupporting

confidence: 54%

Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Nir-Arad,

Shlomi,

Manukovsky

et al. 2023

J. Am. Chem. Soc.

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“…In this study, we focus on systems containing high concentrations of trityl or BDPA radicals as test systems that have been reported to form electron spin clusters and give rise to DNP enhancement of 1 H NMR and signatures indicating that multiple coupled electron spins are involved in the transfer process. ,− The DNP enhancement versus microwave (μw) irradiation frequency measured at 15 K and 6.9 T for trityl-OX063 vitrified (35 mM) in water–DMSO solution is shown in Figure . The DNP profile is acquired at two different μw powers, 100 and 350 mW.…”

mentioning

confidence: 99%

“…They include the photoactivated electron spin clusters in quantum dots or defect centers, 49 and P1 or NV centers that have been recently shown to interact with each other via exchange coupling. 27 , 28 …”

mentioning

confidence: 99%

Dipolar Order Induced Electron Spin Hyperpolarization

Equbal,

Ramanathan,

Han

2024

J. Phys. Chem. Lett.

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The structure of coupled electron spin systems is of fundamental interest to many applications, including dynamic nuclear polarization (DNP), enhanced nuclear magnetic resonance (NMR), the generation of electron spin qubits for quantum information science (QIS), and quantitative studies of paramagnetic systems by electron paramagnetic resonance (EPR). However, the characterization of electron spin coupling networks is nontrivial, especially at high magnetic fields. This study focuses on a system containing high concentrations of trityl radicals that give rise to a DNP enhancement profile of 1H NMR characteristic of the presence of electron spin clusters. When this system is subject to selective microwave saturation through pump–probe ELectron DOuble Resonance (ELDOR) experiments, electron spin hyperpolarization is observed. We show that the generation of an out-of-equilibrium longitudinal dipolar order is responsible for the transient hyperpolarization of electron spins. Notably, the coupled electron spin system needs to form an AX-like system (where the difference in the Zeeman interactions of two spins is larger than their coupling interaction) such that selective microwave irradiation can generate signatures of electron spin hyperpolarization. We show that the extent of dipolar order, as manifested in the extent of electron spin hyperpolarization generated, can be altered by tuning the pump or probe pulse length, or the interpulse delay in ELDOR experiments that change the efficiency to generate or readout longitudinal dipolar order. Pump–probe ELDOR with selective saturation is an effective means for characterizing coupled electron spins forming AX-type spin systems that are foundational for DNP and quantum sensing.

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“…While the orientations of the two electron spin packets that overlap might end up having matching, fast electron spin–lattice relaxation times, it is the spin packets with their dipolar coupling vector orientation giving rise to EPR frequency shifts with respect to the center frequency of the isolated electron spin by the nuclear larmor frequency that matter for ESC-DNP by resonance matching. In fact, a sharp contrast in spin–lattice relaxation times between the sensitizer populations and the clustered radical populations can give rise to a positive or negative absorptive central DNP profile feature via the truncated Cross Effect (tCE) mechanism. − Such an absorptive feature is advantageous for NMR signal amplification under MAS where the positive and negative dispersive features could otherwise cancel out due to oscillatory broadband irradiation of the entire EPR spectrum unless special pulse sequences and irradiation schemes and timings are employed. These qualities give ESC-DNP even further design scope and potential for efficient enhancement at high fields with low power.…”

mentioning

confidence: 99%

Dynamic Nuclear Polarization Using Electron Spin Cluster

Chaklashiya,

Equbal,

Shernyukov

et al. 2024

J. Phys. Chem. Lett.

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Dynamic nuclear polarization (DNP) utilizing narrow-line electron spin clusters (ESCs) to achieve nuclear spin resonance matching (ESC-DNP) by microwave irradiation is a promising way to achieve NMR signal enhancements with a wide design scope requiring low microwave power at high magnetic field. Here we present the design for a trityl-based tetra-radical (TetraTrityl) to achieve DNP for 1H NMR at 7 T, supported by experimental data and quantum mechanical simulations. A slow-relaxing (T 1e ≈ 1 ms) 4-ESC is found to require at least two electron spin pairs at <8 Å e–e spin distance to yield 1H ESC-DNP enhancement, while squeezing the rest of the e–e spin distances to <12 Å results in optimal 1H ESC-DNP enhancements. Fast-relaxing ESCs (T 1e ≈ 10 μs) are found to require a weakly coupled narrow-line radical (sensitizer) to extract polarization from the ESC. These results provide design principles for achieving a power-efficient DNP at high field via ESC-DNP.

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P1 Center Electron Spin Clusters Are Prevalent in Type Ib Diamonds

Cited by 9 publications

References 71 publications

Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Dipolar Order Induced Electron Spin Hyperpolarization

Dynamic Nuclear Polarization Using Electron Spin Cluster

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