All-optical and microwave-free detection of Meissner screening using nitrogen-vacancy centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-13 |
| Journal | Journal of Applied Physics |
| Authors | D. Paone, D. Pinto, G. KIM, Feng L, M. J. Kim |
| Institutions | University of Stuttgart, Ăcole Polytechnique FĂ©dĂ©rale de Lausanne |
| Citations | 15 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Microwave-Free NV Sensing
Section titled âTechnical Documentation & Analysis: Microwave-Free NV SensingâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a significant advancement in nanoscale magnetometry by introducing an all-optical, microwave-free method utilizing Nitrogen-Vacancy (NV) centers in diamond. This approach is highly relevant for engineers and scientists working on quantum sensing and condensed matter physics.
- Core Achievement: Successful detection and spatial mapping of the Meissner screening effect in a superconducting La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) thin film using the magnetic field dependent photoluminescence (PL) of an NV ensemble.
- Methodology Advantage: The technique is entirely microwave-free (non-resonant), eliminating local heating effects that often plague traditional Optically Detected Magnetic Resonance (ODMR) methods, making it ideal for sensitive superconducting samples.
- Quantitative Results: The critical current density (j$_{c}$) of the 20 nm LSCO film was accurately quantified as 1.4 * 10$^{8}$ A/cm$^{2}$ by fitting the spatial magnetic field profile using Brandtâs analytical model.
- Material Requirement: The method relies critically on high-quality, thin Single Crystal Diamond (SCD) membranes for NV implantation to ensure close proximity (approx. 1 ”m) to the sample surface, maximizing sensitivity.
- Future Potential: The technique is scalable and can be combined with optical pump-probe spectroscopy to study time-resolved dynamical phenomena, such as vortex formation and motion, in Type II superconductors.
- 6CCVD Value: 6CCVD provides the necessary ultra-pure, custom-thickness SCD material and precision polishing required to replicate and extend this high-resolution quantum sensing platform.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the analysis of the Meissner screening experiment:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Superconductor Critical Temperature (T$_{c}$) | 34 | K | LSCO thin film |
| Applied Magnetic Field (B$_{z}$) | 4.2 | mT | External field for screening detection |
| First Critical Field (H$_{c1}$) | ~2 | mT | SQUID measurement |
| Critical Current Density (j$_{c}$) | 1.4 * 10$^{8}$ | A/cm$^{2}$ | Extracted using Brandtâs model |
| LSCO Film Thickness (d) | 20 | nm | Superconducting layer |
| NV Excitation Wavelength | 512 | nm | Pulsed Green Laser |
| NV Emission Wavelength | 637 - 750 | nm | Red Photoluminescence (PL) |
| NV Zero Field Splitting (D) | 2.87 | GHz | ODMR calibration |
| Magnetic Field Screening | ~56 | % | Reduction observed inside LSCO |
| NV-SC Distance | ~1 | ”m | Distance between sensor and sample |
| Base Cryostat Pressure | 3 * 10$^{-10}$ | mbar | UHV operating condition |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully demonstrated microwave-free NV magnetometry through the following steps:
- Sample Preparation: An NV implanted diamond membrane was physically attached to the edge of a 20 nm thick LSCO thin film grown epitaxially on a LaSrAlO$_{4}$ (LSAO) substrate.
- Cryogenic Operation: All measurements were conducted using a confocal microscope integrated with an UHV-He bath cryostat operating at a base temperature of 4.2 K.
- Optical Excitation: NV centers were excited using a 512 nm pulsed green laser, and the resulting red photoluminescence (PL) was recorded with a photon detector.
- Magnetic Field Application: An external magnetic field (B$_{z}$ = 4.2 mT) was applied along the z-direction using a 3D vector magnet.
- Microwave-Free Detection: Meissner screening was detected by measuring the relative drop in NV PL yield, which is highly dependent on the off-axis magnetic field strength, thereby avoiding resonant microwave excitation.
- Calibration: ODMR spectroscopy was used separately and solely for the quantitative calibration of the absolute magnetic field strength corresponding to the observed PL drop percentages.
- Data Analysis: The spatial variation of the magnetic field profile across the LSCO edge was raster-scanned and fitted using Brandtâs analytical model to extract the critical current density (j$_{c}$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for high-quality, precisely engineered diamond materials for advanced quantum sensing applications. 6CCVD is uniquely positioned to supply the necessary Single Crystal Diamond (SCD) and customization services required to replicate and advance this microwave-free NV magnetometry platform.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high sensitivity and low noise required for nanoscale magnetic field detection, the following 6CCVD material is essential:
- Optical Grade Single Crystal Diamond (SCD): Required for NV center formation. Our SCD material offers ultra-low strain and high purity, ensuring optimal spin coherence times necessary for sensitive quantum measurements.
- Ultra-Thin SCD Substrates: The experiment requires the NV sensor to be within ~1 ”m of the sample surface. 6CCVD provides SCD wafers with precise thickness control, enabling the fabrication of ultra-thin membranes necessary for maximizing magnetic field coupling.
Customization Potential
Section titled âCustomization PotentialâThe successful implementation of this technique depends on precise material geometry and surface quality, areas where 6CCVD excels:
| Research Requirement | 6CCVD Customization Capability | Benefit to the Engineer |
|---|---|---|
| Thin Membrane Fabrication | SCD Thickness Control (0.1 ”m - 500 ”m) | Allows researchers to specify the exact membrane thickness required for optimal NV implantation depth and mechanical stability. |
| Close Proximity Sensing | Ultra-Smooth Polishing (Ra < 1 nm) | Our superior polishing ensures minimal surface roughness, critical for achieving the necessary ~1 ”m sensor-to-sample distance and minimizing signal loss. |
| Integration into Cryostats | Custom Dimensions & Laser Cutting | We provide custom laser cutting services for precise membrane geometries, facilitating integration into complex UHV-Cryostat and confocal microscopy setups. |
| Future Integrated Devices | Custom Metalization (Au, Pt, Ti, Cu, W) | For extensions involving integrated microwave lines (if ODMR is later required) or electrical contacts, 6CCVD offers in-house metalization capabilities. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in diamond material science for quantum applications. We offer authoritative professional support for projects requiring:
- Material Selection: Assistance in selecting the optimal SCD grade and thickness for specific NV implantation recipes (e.g., shallow NV layers for enhanced surface sensitivity).
- Surface Preparation: Consultation on achieving the necessary surface termination and roughness (Ra < 1 nm) for membrane bonding and high-resolution imaging.
- Similar Projects: Support for similar nanoscale magnetic field sensing projects, including those focused on vortex dynamics, ferromagnetism, or non-equilibrium phase transitions in 2D materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Microscopic studies on thin film superconductors play an important role for probing non-equilibrium phase transitions and revealing dynamics at the nanoscale. However, magnetic sensors with nanometer scale spatial and picosecond temporal resolution are essential for exploring these. Here, we present an all-optical, microwave-free method that utilizes the negatively charged nitrogen-vacancy (NV) center in diamond as a non-invasive quantum sensor and enables the spatial detection of the Meissner state in a superconducting thin film. We place an NV implanted diamond membrane on a 20nm thick superconducting La2âxSrxCuO4 (LSCO) thin film with Tc of 34K. The strong B-field dependence of the NV photoluminescence allows us to investigate the Meissner screening in LSCO under an externally applied magnetic field of 4.2mT in a non-resonant manner. The magnetic field profile along the LSCO thin film can be reproduced using Brandtâs analytical model, revealing a critical current density jc of 1.4Ă108A/cm2. Our work can be potentially extended further with a combination of optical pump probe spectroscopy for the local detection of time-resolved dynamical phenomena in nanomagnetic materials.