In one minute

Mankowsky, Subedi and colleagues investigate how resonant mid-infrared excitation changes the crystal structure of YBa2Cu3O6.5, rather than directly measuring a new equilibrium superconducting transition. They drive a lattice vibration and probe four Bragg reflections with 50-femtosecond X-ray pulses at 100 K, above the sample’s 52 K equilibrium transition. Fitting the diffraction measurements with calculated phonon displacements yields expansion within copper-oxide bilayers, contraction between bilayers and increased bond buckling. Density-functional calculations predict accompanying electronic changes that the authors consider favorable to superconductivity. The structural response lasts only picoseconds, and its relationship to earlier optical signatures of enhanced interlayer transport motivates further electronic measurements and a full many-body treatment.

Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5