Uncovering origins of heterogeneous superconductivity in La3Ni2O7
Summary
This Nature paper uses wide-field nitrogen-vacancy (NV) microscopy embedded in diamond anvil cells to map superconductivity, stress and chemistry in single-crystal La3Ni2O7 at sub-μm resolution under high pressure. By combining optically detected magnetic resonance (ODMR) imaging of the local diamagnetic (Meissner) response, pixel-registered stress-tensor maps and energy-dispersive X-ray (EDX) stoichiometry, the authors build local, multimodal phase diagrams and identify the drivers of spatially heterogeneous superconductivity.
Key experimental findings: local superconducting pockets nucleate where the normal stress (σZZ) is high, superconductivity is quenched above a critical shear stress (τ ≈ 2 GPa), stoichiometry close to La:Ni = 3:2 is required for diamagnetism, and trapped flux is observed in the same regions that show the Meissner response. The approach yields a three-dimensional superconducting dome in (T, σZZ, τ) and explains why many samples show filamentary or spatially inhomogeneous superconductivity.
Key Points
- Wide-field NV magnetometry in a diamond anvil cell images local Meissner effect and trapped flux in La3Ni2O7 with sub-μm resolution, simultaneously with four-probe transport.
- Local diamagnetism and the first resistance drops are spatially correlated; superconducting regions appear before the whole sample shows zero resistance.
- Superconductivity first appears in regions of elevated normal stress (σZZ); reported bulk onset pressures mask large local variations.
- Shear stress strongly suppresses superconductivity: above a critical shear ~2 GPa the superconducting response is quenched.
- Chemical stoichiometry matters: local La:Ni ≈ 3:2 regions show the strongest diamagnetic response; off-stoichiometry stripes do not superconduct locally.
- Measured superconducting volume fractions are very small (S1 ≈ 3%, S2 ≈ 0.3%, S3 ≈ 0.5%), consistent with previously reported filamentary behaviour.
- The multimodal method converts sample inhomogeneity into a resource, producing continuous, pixel-level phase diagrams in T, normal stress and shear stress.
Context and relevance
Nickelates are central to efforts to understand unconventional high-Tc superconductivity and their relation to cuprates. La3Ni2O7 is especially notable because it superconducts at high temperatures under pressure, but results across groups have been inconsistent. This work provides a spatially resolved explanation: local mechanical and chemical inhomogeneity — not a single bulk pressure — controls where and when superconductivity appears. That matters for reproducibility, interpretation of transport-only measurements and for designing experiments or devices that aim to exploit nickelate superconductivity.
Why should I read this?
Short answer: because it actually tells you why different labs see different La3Ni2O7 results. Fancy quantum sensors let the authors map where superconductivity lives (and where it doesn’t) and pin the blame mostly on local stress and stoichiometry. If you care about nickelates, high‑pressure experiments, or why superconductivity looks ‘filamentary’ in real samples, this paper saves you a stack of guesswork and points to what to fix in sample prep and pressure media.
Author style
Punchy: this is high-impact, hands-on metrology. The paper isn’t just another report of a transition temperature — it rewrites how we should think about pressure as a continuous, spatially varying tuning knob and shows a clear mechanism (shear + chemistry) behind heterogeneous superconductivity. If you follow nickelates or high-pressure techniques, read the full paper for the data and methods — they matter.
Source
Article Date: 25 February 2026
Article URL: https://www.nature.com/articles/s41586-025-10095-x
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