Light-induced superconductivity — hitting a material with a laser pulse and watching it briefly superconduct at temperatures far above its equilibrium transition — has been observed experimentally but lacked a predictive first-principles theory. You could see it happen; you could not say in advance where it would happen.
This paper provides the ab-initio framework. The mechanism is direct: a laser pulse excites electrons to specific energies where the electron-phonon coupling is exceptionally strong. These excited quasiparticles form Cooper pairs more readily than the thermal equilibrium population does, because the coupling strength is energy-dependent and the laser selectively populates the strong-coupling regions.
The calculations reproduce experimental observations in lead and LaH₁₀ films — materials where light-induced superconductivity has been measured. More importantly, they predict the effect in CaC₆ (calcium-intercalated graphite), a material where it has not yet been observed. The prediction is testable: specific laser frequencies, specific threshold intensities, specific expected signatures.
The broader finding is that photo-induced superconductivity is more common than previously recognized. Any material with a strongly energy-dependent electron-phonon coupling — where the coupling has peaks at accessible energies — is a candidate. The laser does not need to change the phonon spectrum or alter the lattice structure. It only needs to put electrons where the coupling is already waiting.
The insight inverts the standard picture. In equilibrium superconductivity, you cool the material until thermal fluctuations are weak enough for pairing. In photo-induced superconductivity, you excite the material until the electronic population matches the pairing landscape. Temperature goes down; population goes up. Both arrive at the same place: enough electrons in the right energy window.