Photo-induced superconductivity

Photo-induced superconductivity is where light is used to induce superconducting-like states in materials.

If we can learn more about the mechanisms behind this phenomenon, we can more intentionally design a room-temp superconductor.

Key Experimental Findings:

1. First discovered in cuprate superconductors (like YBa₂Cu₃O₆.5) when excited with specific wavelengths of infrared light

2. Later observed in other materials including:

   • Organic molecular crystals (particularly K₃C₆₀)

   • Rare-earth nickelates

   • Certain quantum materials

Common Features:

• Usually triggered by mid-infrared or terahertz pulses that target specific lattice vibrations

• The effect often appears at temperatures well above the material's normal superconducting transition temperature

• Shows characteristic superconducting properties like perfect conductivity and Meissner-like diamagnetic response

Timescales:

• Early experiments showed effects lasting only femtoseconds to picoseconds

• Recent work has achieved longer-lived states in the nanosecond regime

  Evidence for metastable photo-induced superconductivity in K3C60

  Authors make use of a new optical device to drive metallic K3C60 with mid-infrared pulses of tunable duration, ranging between one picosecond and one nanosecond. The same superconducting-like optical properties observed over short time windows for femtosecond excitation are shown here to become metastable under sustained optical driving, with lifetimes in excess of ten nanoseconds. https://www.nature.com/articles/s41567-020-01148-1

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• The holy grail would be achieving stable room-temperature superconductivity through this mechanism

Current Understanding of Mechanisms:

• Light can modify the crystal structure through targeted excitation of phonon modes

• This structural modification can enhance electron pairing

• The exact mechanism is still debated, with competing theories about:

  • Phonon-mediated coupling

  • Enhanced electron correlations

  • Modified electronic structure

  • Dynamical stabilization of Cooper pairs

Challenges:

• Making the state persist longer

• Understanding the fundamental physics

• Achieving the effect with less intense light