More proof that the evidence for photoinduced superconductivity in K₃C₆₀ is distorted

We recently identified a large systematic error that corrupts the evidence for photoinduced superconductivity in K₃C₆₀. Most of this evidence has come from time-resolved terahertz (TR-THz) spectroscopy, which is sensitive to the nonequilibrium electrodynamic response of materials at the relevant frequencies and timescales. However, TR-THz directly measures the complex reflection amplitude r(ω), not the local nonequilibrium complex conductivity σ(ω). To relate them, one needs to specify the complex photoconductivity depth profile Δσ(ω, z), which typically is not known independently. We showed that at the high excitation densities employed in photinduced superconductivity experiments, the photoconductivity depth profile must be distorted from the profile originally used to interpret the experiments. When we correct for this distortion, we obtain nonequilibrium conductivity spectra that are qualitatively different from those originally reported. The corrected results are consistent with a model in which photoexcitation enhances the carrier mobility but does not produce superconductivity. In this presentation, I will discuss more recent results that provide additional support for our reinterpretation.