Picosecond Pulses Reveal Superconductivity's Hidden Breaking Point

Researchers at MPSD used few-picosecond current pulses to outrun vortex motion and heating, reaching the depairing current in superconductors. NbN broke down sharply while YBCO weakened gradually, reflecting their s-wave and d-wave gap symmetries.

• Photoconductive switches driven by 300-fs, 515-nm green laser pulses generate the currents
• Pulses last picoseconds, so vortices move only tens of nanometers
• NbN failed at a sharp threshold; YBCO degraded progressively due to its d-wave gap
• The method probes microscopic superconductor properties inaccessible to DC transport