Giant Resonant Enhancement for Photo-induced Metastable Superconductivity in K₃C₆₀

The search for new non-equilibrium functional phases in quantum materials has become a central research theme in condensed matter physics. In the alkali doped fulleride K₃C₆₀, photo-excitation close to resonance of on-ball molecular vibrations has been shown to induce a transient state with superconducting-like optical properties up to 100K, far above the equilibrium transition temperature Tc = 20K.

In this talk I will first describe recent experiments which have extended the lifetime of the transient superconducting-like state up to several nanoseconds, rendering this state metastable. GHz-frequency electrical transport measurements carried out in the metastable regime revealed the onset of a state with vanishingly-low resistance.

Furthermore, a dominant energy scale for this phenomenon was recently discovered by tuning the drive frequency to 10THz. At this frequency, metastable photo-induced superconductivity is observed up to room temperature for fluences as low as 400 µJ/cm². This corresponds to a two order of magnitude enhancement in photo-susceptibility, allowing for a significant reduction in dissipation and tracing a path towards steady state operation.