Superheating field of a superconductor under GHz radio-frequency drive
In plain words
The superheating field is calculated for a steady field, but cavity fields oscillate a billion times per second. Whether the limit is higher, lower or the same under such fast oscillation is not settled.
Precise statement
Compute the dynamic superheating field $H_{\mathrm{sh}}(f,T)$ for an s-wave superconductor driven at $f\sim 0.1\text{ to }10\,\mathrm{GHz}$, including nonequilibrium quasiparticles and the finite vortex nucleation time, using nonequilibrium quasiclassical (Keldysh-Usadel or Eilenberger) dynamics valid at $T << T_{c}$; time-dependent Ginzburg-Landau theory may be used only as a check near $T_{c}$. An answer gives $H_{\mathrm{sh}}(f,T)/H_{\mathrm{sh}}(0,T)$ for Nb and Nb3Sn and the frequency at which it departs from the static value.
What would settle it
A microscopic nonequilibrium calculation checked against pulsed RF measurements of the quench field versus frequency and pulse length.