CM In the literature: open

Does photoexcited K3C60 above $T_{c}$ expel magnetic field

In plain words

Superconductors push out magnetic fields (the Meissner effect). A measurement on light-driven K3C60 has so far only set a limit on this effect.

Precise statement

Measure the transient volume susceptibility $\chi_v$ of K3C60 at $T > 20\ \mathrm{K}$ after mid-infrared excitation; complete expulsion is $\chi_v = -1/(4\pi)$ in CGS, reduced by the excited volume fraction. Answer yes or no: is $\chi_v(t, T)$ distinguishable from zero within its uncertainty and consistent with superconducting diamagnetism of the excited volume?

What would settle it

Time-resolved magneto-optic or nitrogen-vacancy magnetometry on single crystals or dense films with better field resolution than the 2025 powder measurement.

Status in the literature

Unverified note

A 2025 Faraday-rotation search on powders (De Vecchi et al., arXiv:2502.20276) bounded the response to less than about 10 percent of complete expulsion, which does not decide the question.