Revision 1

Superseded · first revision · record

Title: Does photoexcited K3C60 above $T_{c}$ expel magnetic field
Plain: 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: 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?
Settled by: Time-resolved magneto-optic or nitrogen-vacancy magnetometry on single crystals or dense films with better field resolution than the 2025 powder measurement.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status 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.
Posed since: (empty)