The emergence of the Abrikosov lattice in the normal phase of type-II superconducting films as the magnetic field approaches the critical field $H_{c2}$ from above was predicted in Glatz et al. [Fluctuation spectroscopy of disordered two-dimensional superconductors, Phys. Rev. B 84, 104510 (2011)]. In the quantum fluctuation regime [Galitski and Larkin, Superconducting fluctuations at low temperature, Phys. Rev. B 63, 174506 (2001)], it is characterized by the formation of relatively large (${\xi }_{\mathrm{QF}}\sim {\xi }_{\mathrm{BCS}}/\sqrt{\tilde{h}}$, $\tilde{h}=H/H_{c2}-1$) and long-lived (${\tau }_{\mathrm{QF}}\sim {\tau }_{\mathrm{\Delta }}/\tilde{h}$, ${\tau }_{\mathrm{\Delta }}=\hslash /\mathrm{\Delta }$) clusters of rotating fluctuation Cooper pairs, representing precursors of Abrikosov vortices. We show that these fluctuation-induced vortex clusters can be detected through their high-frequency electromagnetic response. Specifically, they produce a pronounced enhancement of the imaginary part of the ac conductivity at characteristic frequencies ${\omega }_{QF}\sim \tilde{h}/{\tau }_{\mathrm{\Delta }}$, arising directly from quantum fluctuations, being well below the superconducting threshold at $2/{\tau }_{\mathrm{\Delta }}$. For niobium, ${\omega }_{QF}$ falls within the experimentally accessible microwave range, making this effect directly testable using modern microwave spectroscopy.

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• Superconducting fluctuations
• Superconductivity
• Vortices in superconductors
• Type-II superconductors
• Diagrammatic methods