# Japanese team computes superconductor coherence and penetration lengths from first principles

- Published: 2026-11-09 03:36 UTC
- Section: Science › Physics
- Tags: coherence length calculation, London penetration depth, first-principles superconductivity, Cooper pairs finite momentum, Uemura plot, H3S high pressure, type-I and type-II superconductors, depairing current
- URL: https://realtech.media/news/rt-72869f02a343d8a55885ff6e_japanese_team_computes/

**The SCDFT-based method yields Tc, coherence length and London penetration depth in one framework without experimental inputs; tested on eight known conventional superconductors.**

![Japanese team computes superconductor coherence and penetration lengths from first principles](https://realtech.media/media/2026/11/85cdb4290d8745b8.webp)
*xenospectrum*

A group from Yokohama National University, Tokyo Metropolitan University, the University of Würzburg and the University of Tokyo has developed a first-principles method for computing the coherence length ξ0 and the London penetration depth λL of superconductors, as reported in Physical Review Letters [1]. The method is built on superconducting density functional theory (SCDFT) and determines ξ0, λL and the transition temperature Tc consistently, without parameters fitted to experiment [1]. The authors tested it on eight known superconductors, and the work is a computational method checked against existing data, not a new material or a device.

## How the lengths are obtained

Conventional SCDFT assumes Cooper pairs are uniformly distributed over the crystal, which makes the lengths hard to access directly. The authors give the pairs a finite centre-of-mass momentum Q and compute the superconducting gap Δ(Q) and the supercurrent density J(Q) as functions of temperature and Q [1]. The coherence length follows from how the gap decays with Q, using Ginzburg–Landau relations that strictly hold near Tc. The penetration depth is found either from the initial slope of J(Q) or from the depairing current at the maximum of J(Q) combined with ξ0. The relevant lengths reach 100–1000 lattice constants, so momenta below 0.1% of the reciprocal lattice vector had to be sampled.

## Comparison with experiment

The test set was Al, Nb, Sn, In, Ta, Pb, V3Si and H3S at about 200 GPa. The method reproduced the type-I/type-II classification for all of them [1]. For niobium, the calculated Tc is 8.09 K against 9.50 K measured; ξ0 is 34 nm against 39±1 nm; λL is 34–40 nm against 27–39 nm in the cited experiments. For H3S the authors obtained Tc of 181 K (experiment: 184 K), ξ0 of 3.0 nm and λL of 19–22 nm, without accounting for lattice anharmonicity. The largest deviation is in aluminium: ξ0 of 636 nm against 1,600 nm measured, and Tc of 1.61 K against 1.140 K.

The lengths also allowed the authors to build the Uemura plot entirely from first principles. It shows that higher-Tc systems combine strong pairing with large phase stiffness [1]. The calculated depairing current density of niobium, 19×10^7 A/cm², is about 25 times the measured critical current density of 0.75×10^7 A/cm². The method currently covers only phonon-mediated conventional superconductors.

## Sources

1. [Physical Review Letters](https://doi.org/10.1103/lrhl-j9bt)
2. [xenospectrum](https://xenospectrum.com/first-principles-superconductor-lengths-computation)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-72869f02a343d8a55885ff6e_japanese_team_computes/