A 6 October 2026 addendum revisits how researchers extracted magnetic-field penetration values from measurements of hydrogen-rich compounds under extreme pressure. Its key point is methodological: identifying where a sample’s initial, approximately linear magnetic response changes is difficult when the pressure cell adds its own magnetic signal and the instrument becomes noisier at higher fields. The addendum’s authors interpret the measured hysteresis loops as evidence of superconductivity, but that interpretation remains disputed.
What does the addendum update?
The addendum by Minkov and coauthors revisits the magnetic-screening analysis in their 2022 study of hydrogen sulfide-derived H3S and lanthanum hydride LaH10. The original work used SQUID magnetometry inside miniature diamond anvil cells. The update focuses on how the field-penetration threshold is identified from magnetization-versus-applied-field data, rather than presenting the reported material parameters as simple, direct readings. Read the 2026 addendum and the 2022 article.
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In the measurement, researchers track magnetization while sweeping an applied magnetic field. They identify an initial, approximately linear Meissner-region trend, then estimate the penetration field from the point where the virgin magnetization curve departs from that trend. The estimated point therefore depends on how that initial trend and its departure are determined; it is not a sharp boundary read off independently of analysis.
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Why is the penetration point difficult to extract?
The diamond anvil cell adds its own signal
The superconducting sample is held in a miniature pressure cell, whose materials contribute a magnetic background. Separating that response from the sample’s signal is part of interpreting the curve. The addendum says this nonlinear cell background complicates parameter estimates, especially when deciding whether an apparent departure from the initial trend marks field penetration.
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Higher-field measurements are noisier
The authors also identify increased noise in the SQUID system’s higher-field range. A noisy curve makes the departure point less certain, so the fitting range and the way the trend is extrapolated matter. The addendum discusses these limitations alongside the demagnetizing correction used in estimating penetration-field values.
For the reported measurements, the applied field was swept from −1 to +1 tesla, with measurements repeated several times at each temperature. The study reports H3S measurements at approximately 155 ± 5 GPa and LaH10 at approximately 130 ± 8 GPa. These are measurements on tiny samples in a challenging instrument environment, not routine bulk-sample magnetometry.
What values did the 2022 study report?
The following are estimates reported in the 2022 study and discussed in the addendum. They depend on the measurement and analysis choices described above; they should not be read as universal constants for every sample or experimental setup.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11| Quantity | H3S | LaH10 |
|---|---|---|
| Estimated zero-temperature lower critical field | Approximately 0.82 T | Approximately 0.55 T |
| Estimated London penetration depth | Approximately 20 nm | Approximately 30 nm |
| Upper critical field estimate used in the analysis | Approximately 97 T | Approximately 143.5 T |
| Reported Ginzburg–Landau parameter | Approximately 12 | Approximately 20 |
These figures are from Minkov and coauthors’ 2022 Nature Communications study. In particular, the London penetration depths and Ginzburg–Landau parameters are derived quantities, not separate direct measurements. The 2022 paper described its miniature diamond-anvil-cell design as capable of reaching pressures as high as 220 GPa; that is a reported design capability, not the pressure of every measurement in the table.
How does SQUID magnetometry compare with other approaches?
Magnetic susceptibility measurements offer an independent route to testing superconductivity and estimating magnetic properties, but the tiny sample and cell background create a persistent signal-separation challenge. A 2024 review discusses SQUID magnetometry, coil-based susceptibility, and nitrogen-vacancy (NV) sensing using diamond anvils. These approaches provide different kinds of information; the available review does not establish one as a universal replacement for the others.
| Approach | What it can probe | Sample signal versus cell background | Pressure and temperature range; information scale |
|---|---|---|---|
| SQUID magnetometry | Magnetization and susceptibility as applied field changes; the 2022 study used curves to estimate a penetration field. | The addendum identifies the cell’s nonlinear magnetic background and increased higher-field noise as complications. | For the measurements discussed here: H3S at approximately 155 ± 5 GPa and LaH10 at approximately 130 ± 8 GPa. A bulk-versus-local characterization is not stated in the 2024 review. |
| Coil-based susceptibility | Susceptibility response. | Not stated in the 2024 review. | Pressure and temperature range and bulk-versus-local characterization are not stated in the 2024 review. |
| NV sensing with diamond anvils | Local magnetic response sensed using nitrogen-vacancy centers in diamond. | Not stated in the 2024 review. | Pressure and temperature range are not stated in the 2024 review; the approach provides local rather than bulk information. |
The method descriptions and qualifications in this comparison are based on the 2024 National Science Review article. It also explains why a textbook picture of complete field expulsion can be hard to apply: strong vortex pinning may make the Meissner effect subtle or barely observable in H3S and LaH10, while trapped magnetic flux can remain after the external field is removed.
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Do the magnetic measurements settle whether these hydrides superconduct?
No consensus is established by these papers. Minkov and coauthors state in the 2026 addendum that “the hysteresis loops recorded in H3S and LaH10 (Figs. 1, 2) unambiguously confirm the superconducting state in these highly compressed hydrides.” Their conclusion is an interpretation of the loops and associated measurements.
By contrast, J. E. Hirsch and F. Marsiglio’s 2023 published critique argues that magnetic measurements reported for hydrides under pressure do not establish superconductivity. The disagreement is about what the magnetic evidence warrants, not about whether the addendum revisits the analysis. Readers should distinguish the authors’ affirmative interpretation from the existence of a published challenge; the addendum does not, by itself, make that interpretive dispute disappear. Read the 2023 critique.
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