Magnetic flux trapping in hydrogen-rich high-temperature superconductors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-06-15 |
| Journal | Nature Physics |
| Authors | Vasily S. Minkov, Vadim Ksenofontov, Sergey L. Budâko, E. F. Talantsev, M. I. Eremets |
| Institutions | Max Planck Institute for Chemistry, M.N. Mikheev Institute of Metal Physics |
| Citations | 72 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Magnetic Flux Trapping in High-Temperature Superconductors
Section titled âTechnical Documentation & Analysis: Magnetic Flux Trapping in High-Temperature SuperconductorsâThis document analyzes the research paper âMagnetic flux trapping in hydrogen-rich high-temperature superconductorsâ published in Nature Physics. It extracts key technical data and links the experimental requirementsâparticularly the need for high-quality, robust, and magnetically inert diamond materialsâto the specialized capabilities of 6CCVD.
Executive Summary
Section titled âExecutive SummaryâThe research introduces a highly sensitive, non-conventional trapped flux method for studying high-temperature superconductivity (HTS) in hydrogen-rich materials under extreme pressure, yielding critical data previously inaccessible via standard techniques.
- Methodological Advance: Implementation of a trapped magnetic flux protocol in a SQUID magnetometer, effectively cancelling the large magnetic background signal originating from the Diamond Anvil Cell (DAC).
- Record HTS Probed: Successfully confirmed superconductivity in near-room-temperature hydrides: Im-3m-H${3}$S ($T{c} \approx 195$ K) and C2/m-LaH${10}$ ($T{c} \approx 200$ K).
- Vortex Dynamics: Demonstrated extremely strong vortex pinning in H$_{3}$S, evidenced by the absence of a pronounced Meissner effect and an ultra-low magnetic flux decay rate (creep).
- Critical Parameters Determined: Derived fundamental characteristics including the lower critical field ($\mu_{0}H_{c1} \approx 0.36$ T) and the London penetration depth ($\lambda_{L} \approx 37$ nm).
- Ultra-High Critical Current Density: Calculated a zero-temperature critical current density ($j_{c}(0)$) of $7.3 \times 10^{10}$ A m$^{-2}$ for H${3}$S, significantly exceeding values found in conventional low-$T{c}$ superconductors.
- Material Sensitivity: The technique is ideal for studying micrometre-sized samples, multiphase systems, and materials with low superconducting fractions, making it a powerful screening tool for novel HTS materials.
- Diamond Requirement: The success of the SQUID/DAC setup relies critically on the mechanical integrity and ultra-low magnetic impurity profile of the diamond anvils used to contain pressures up to 167 GPa.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the study, primarily concerning the Im-3m-H$_{3}$S phase.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Critical Temperature ($T_{c}$) | 195 ± 5 | K | Im-3m-H$_{3}$S phase at 155 GPa |
| Critical Current Density ($j_{c}(0)$) | 7.3 $\times$ 10$^{10}$ | A m$^{-2}$ | Extrapolated to 0 K for H$_{3}$S |
| Lower Critical Field ($\mu_{0}H_{c1}(10 K)$) | 0.36 (0.32-0.48) | T | Estimated for H$_{3}$S (10 K) |
| Full Penetration Field ($\mu_{0}H^{*}$) | 0.70 ± 0.05 | T | Saturation field (FC mode) |
| London Penetration Depth ($\lambda_{L}(10 K)$) | 37 (31-40) | nm | Estimated for H$_{3}$S |
| Ginzburg-Landau Parameter ($\kappa(10 K)$) | 20 (17-22) | - | Estimated for H$_{3}$S |
| Coherence Length ($\xi(10 K)$) | 1.85 | nm | Used for $\lambda_{L}$ calculation |
| Maximum Pressure (H$_{3}$S) | 155 ± 5 | GPa | Measurement condition |
| Sample Thickness (H$_{3}$S) | $\approx$ 2.8 | ”m | Disc-shaped sample |
| Magnetic Flux Decay Rate | 2.8% | % / 53.6 hours | Measured at 165 K (Extremely slow creep) |
| Applied Magnetization Field ($\mu_{0}H_{M}$) | 0.5 - 6.0 | T | Range used for flux trapping |
Key Methodologies
Section titled âKey MethodologiesâThe experiment combined extreme high-pressure synthesis with highly sensitive magnetic measurements, relying on specialized diamond anvil cell (DAC) components.
- Sample Synthesis: Sandwiched samples (S + NH${3}$BH${3}$ or LaH${3}$ + NH${3}$BH$_{3}$) were molded into thin plates (6-8 ”m thick) and loaded into a miniature DAC.
- Pressurization: Samples were pressurized to 155 GPa (H${3}$S) or 120-130 GPa (LaH${10}$). Pressure gradients across the culet were estimated at $\pm$7 GPa.
- High-Temperature Synthesis: Performed via one-side heating using a Nd:YAG pulse laser ($\lambda$ = 1.064 ”m, 3 ”s pulse duration, 10$^{4}$ Hz frequency). The laser spot diameter was $\approx$ 5 ”m.
- SQUID Setup: Magnetization measurements ($m(T)$) were conducted using a S700X SQUID magnetometer. The miniature DAC was attached to a 140 mm Kapton polyimide straw to minimize end effects.
- Trapped Flux Protocol: Magnetic moment ($m_{trap}(T)$) was measured at zero external field after two primary magnetization protocols:
- ZFC (Zero-Field Cooled): Sample cooled at 0 T, field applied at low temperature ($T_{M}$ = 10 K for H$_{3}$S), held, then field removed.
- FC (Field Cooled): Sample cooled from normal state ($T > T_{c}$) to $T_{M}$ (4 K for H${3}$S) under applied field ($\mu{0}H_{M}$), then field removed.
- Background Management: The DAC magnetic background was determined by measuring the DAC after the sample was decompressed to ambient pressure (non-superconducting state) and applying a linear fit correction.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and extension of this high-pressure, high-sensitivity research hinges on the quality and purity of the diamond materials used in the DAC. 6CCVD is uniquely positioned to supply the necessary MPCVD diamond components that meet the stringent requirements of SQUID magnetometry and extreme pressure physics.
Applicable Materials
Section titled âApplicable Materialsâ| Material Grade | Application in HTS Research | 6CCVD Specification |
|---|---|---|
| Optical Grade SCD | Diamond Anvils/Windows for DACs. Essential for high-pressure containment (up to 167 GPa) and optical access (laser heating, thickness monitoring). | Single Crystal Diamond (SCD) substrates up to 10 mm thick, high mechanical strength, low birefringence. |
| High Purity SCD | Minimizing magnetic background noise in SQUID measurements. Low-impurity diamond is critical to avoid paramagnetic/ferromagnetic interference. | SCD with ultra-low nitrogen and boron content, ensuring minimal magnetic signature at low temperatures and zero field. |
| Boron-Doped Diamond (BDD) | Exploration of alternative high-$T_{c}$ materials or integrated sensors. BDD is a known superconductor with tunable properties. | Custom BDD films (SCD or PCD) with precise doping control for conductivity and superconductivity studies. |
Customization Potential
Section titled âCustomization PotentialâThe study utilized miniature DACs and micrometre-sized samples, requiring exceptional precision in material fabrication. 6CCVDâs in-house engineering capabilities directly address these needs:
- Custom Dimensions and Thickness: We provide SCD plates and wafers with thicknesses ranging from 0.1 ”m up to 500 ”m, and robust substrates up to 10 mm thick, suitable for high-load anvils. We can supply custom plates/wafers up to 125 mm (PCD).
- Precision Geometry for DACs: The paper noted challenges with pressure gradients and diamond cracking. 6CCVD offers advanced laser cutting and shaping services to achieve the precise culet diameters, beveled slopes, and overall geometries required for stable, high-pressure DAC operation.
- Surface Finish: For optimal optical access and consistent pressure distribution across the sample interface, 6CCVD guarantees superior polishing with surface roughness (Ra) less than 1 nm for SCD and less than 5 nm for inch-size PCD.
- Integrated Sensor Metalization: For future experiments integrating electrical transport measurements within the DAC, 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) directly onto the diamond surface, enabling robust electrical contacts under extreme conditions.
Engineering Support
Section titled âEngineering SupportâThe complexity of high-pressure SQUID magnetometry, particularly the selection of diamond materials that are mechanically stable at 167 GPa while remaining magnetically inert, requires specialized expertise.
6CCVDâs in-house PhD team provides authoritative engineering support for projects involving:
- Material Selection: Consulting on the optimal diamond grade (Type IIa, low-impurity SCD) to minimize background noise and maximize mechanical stability in high-pressure SQUID/DAC setups.
- Design Optimization: Assistance with customizing diamond geometry and polishing specifications to mitigate stress concentration and prevent the cracking observed in the reported experiment.
- Advanced Superconductivity Projects: Support for researchers aiming to replicate or extend this Trapped Flux Method for screening new high-temperature superconducting materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Recent discoveries of superconductivity in various hydrides at high pressures have shown that a critical temperature of superconductivity can reach near-room-temperature values. However, experimental studies are limited by high-pressure conditions, and electrical transport measurements have been the primary technique for detecting superconductivity in hydrides. Here we implement a non-conventional protocol for the magnetic measurements of superconductors in a SQUID magnetometer and probe the trapped magnetic flux in two near-room-temperature superconductors H 3 S and LaH 10 at high pressures. Contrary to traditional magnetic susceptibility measurements, the magnetic response from the trapped flux is almost unaffected by the background signal of the diamond anvil cell due to the absence of external magnetic fields. The behaviour of the trapped flux generated under zero-field-cooled and field-cooled conditions proves the existence of superconductivity in these materials. We reveal that the absence of a pronounced Meissner effect is associated with the very strong pinning of vortices inside the samples. This approach can also be a tool for studying multiphase samples or samples that have a low superconducting fraction at ambient pressure.