AC sensing using nitrogen vacancy centers in a diamond anvil cell up ton 6 GPa
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-10-12 |
| Journal | arXiv (Cornell University) |
| Authors | Zhipan Wang, Christopher McPherson, R. Kadado, Nicholas Brandt, S. Edwards |
| Institutions | University of California, Davis, Planetary Science Institute |
| Citations | 8 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated AC magnetic sensing (AC-ODMR) using Nitrogen-Vacancy (NV) centers within a Diamond Anvil Cell (DAC), successfully operating up to 6 GPa.
- Value Proposition: Enables all-optical Nuclear Magnetic Resonance (NMR) detection in nanoliter (nL) sample volumes at extreme pressures, offering a viable alternative to conventional, volume-limited Faraday-induction detection methods.
- Hardware Innovation: A custom straight gold microwave strip antenna (8 ”m thick) was fabricated and integrated onto the anvil culet, insulated from the conducting gasket, to efficiently deliver high H1 fields (tens of MHz Rabi frequency) into the sample space.
- Detection Performance: Achieved a sensitivity of 1.9 nT/âHz at ambient pressure, although this degraded to 7.6 nT/âHz at 3.6 GPa due to pressure-induced issues.
- Limiting Factors: Sensitivity is primarily reduced by microwave field inhomogeneity (H1 distribution width ~40% of average) and pressure gradients (non-hydrostaticity above 3 GPa), which broaden the NV spectrum and damp Rabi oscillations.
- Spectroscopic Results: The technique successfully detected the Larmor precession of 13C nuclear spins in the diamond lattice (~0.3 MHz) and 1H spins in the pressure medium (~1.2 MHz).
- Future Outlook: Utilizing double quantum coherence and shaped microwave pulses is proposed to mitigate inhomogeneous broadening and further enhance sensitivity under strong pressure gradients.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Demonstrated | 5.96 | GPa | NV ensemble spectrum measured by CW. |
| NV Diamond Concentration | 0.3 | ppm | Element 6 crystal used. |
| NV Diamond Dimensions | 100 x 75 x 20 | ”m3 | Crystal size secured to the anvil culet. |
| Typical DAC Sample Volume | 0.1 - 1 | nL | Volume contained within the metallic gasket. |
| External Magnetic Field (H0) | 29 | mT | Oriented 54.7° from vertical along the [111] direction. |
| Required Rabi Frequency (Ω) | > 5 | MHz | Necessary for 90° pulse time of ~50 ns. |
| Microwave Antenna Material | Gold | N/A | 8 ”m thick, 11 ”m wide straight strip. |
| AC Sensing Sensitivity (η) | 1.9 | nT/âHz | Ambient pressure (0 GPa). |
| AC Sensing Sensitivity (η) | 7.6 | nT/âHz | High pressure (3.6 GPa). |
| NV Coherence Time (T2) | ~ 200 | ”s | Limits minimum detectable frequency to ~10 kHz. |
| Zero-Field Splitting (D) Shift | 11.72 | MHz/GPa | Pressure dependence used for calibration. |
| Maximum Detectable Frequency (fmax) | ~ 10 | MHz | Bounded by shortest possible 180° pulse time. |
| Minimum Detectable Frequency (fmin) | ~ 1 | kHz | Bounded by T2 coherence time. |
Key Methodologies
Section titled âKey Methodologiesâ- DAC and NV Crystal Integration: A CryoDAC SC was used. The NV diamond crystal (0.3 ppm NVs, 20 ”m thick) was secured to the anvil culet, aligning the NV [100] axis parallel to the DAC axis.
- Microwave Antenna Fabrication: A straight gold strip antenna (8 ”m thick, 11 ”m wide) was fabricated via electroplating and secured onto the anvil culet using adhesive. Leads were attached with silver epoxy.
- Insulation Layer Application: The gold antenna was insulated from the conducting copper-beryllium gasket using a thin layer of epoxy mixed with aluminum oxide and boron nitride powders, cured under compression.
- Static Magnetic Field (H0) Setup: An external H0 field (29 mT) was applied using fixed neodymium magnets, oriented to align with the NV [111] direction for optimal ODMR contrast.
- Optical Readout System: A long-working distance objective (Nikon CFI T Plan Epi SLWD 50X, N.A. 0.40) was used for 532 nm excitation and fluorescence collection through the transparent diamond anvils.
- Microwave Pulse Generation: Microwave pulse sequences (e.g., Ramsey, XY8-16 dynamical decoupling) were generated using an arbitrary waveform generator (Tabor AWG) and amplified (16 W) to achieve the necessary Rabi frequencies (tens of MHz).
- AC Detection Scheme: Synchronized readout (quantum heterodyne) was implemented, involving coherent averaging of repeated dynamical decoupling sequences, followed by a Fourier transform of the fluorescence contrast (ÎI) to extract the amplitude and frequency of the dynamic magnetic field (Bac).
- Pressure Monitoring: Pressure was continuously tracked by measuring the linear shift of the NV zero-field splitting (D) resonance frequency.
Commercial Applications
Section titled âCommercial Applicationsâ- High-Pressure Materials Science: Characterization of novel materials (e.g., hydrogen-rich superconductors) synthesized in DACs, where sample volumes are too small for conventional NMR.
- Geochemical Research: Testing thermodynamic models and fluid chemistry predictions relevant to the Earthâs mantle and crust (up to 6 GPa and 1200 °C), particularly concerning aqueous carbonate speciation.
- Quantum Sensing Technology: Development of robust, miniaturized quantum sensors capable of operating under extreme hydrostatic and non-hydrostatic pressure environments.
- Micro-NMR Spectroscopy: Enabling high-resolution magnetic resonance spectroscopy on nanoliter or picoliter volumes, applicable to specialized chemical or biological samples.
- Dynamic Nuclear Polarization (DNP) Systems: Integration of NV magnetometry with DNP techniques (using free radicals like TEMPOL) to hyperpolarize nuclear spins in high-pressure liquid solutions, dramatically enhancing signal-to-noise ratios.
- Diamond Anvil Cell (DAC) Engineering: Providing validated designs for integrating high-power, high-frequency microwave delivery systems (straight antennas) into standard DAC setups, overcoming screening effects from conducting gaskets.
View Original Abstract
Nitrogen-vacancy color centers in diamond have attracted broad attention as\nquantum sensors for both static and dynamic magnetic, electrical, strain and\nthermal fields, and are particularly attractive for quantum sensing under\npressure in diamond anvil cells. Optically-based nuclear magnetic resonance may\nbe possible at pressures greater than a few GPa, and offers an attractive\nalternative to conventional Faraday-induction based detection. Here we present\nAC sensing results and demonstrate synchronized readout up to 6 GPa, but find\nthat the sensitivity is reduced due to inhomogeneities of the microwave field\nand pressure within the sample space. These experiments enable the possibility\nfor all-optical high resolution magnetic resonance of nanoliter sample volumes\nat high pressures.\n
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 1996 - High Pressure Experimental Methods [Crossref]