1. Nonlinear lattice dynamics as a basis for enhanced superconductivity in Y[Ba.sub.2][Cu.sub.3][O.sub.6.5]
- Author
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Mankowsky, R., Subedi, A., Forst, M., Mariager, S.O., Chollet, M., Lemke, H.T., Robinson, J.S., Glownia, J.M., Minitti, M.P., Frano, A., Fechner, M., Spaldin, N.A., Loew, T., Keimer, B., Georges, A., and Cavalleri, A.
- Subjects
Engineering research ,Crystals -- Structure ,Superconductivity -- Research ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures (1-3). In complex oxides, this method has been used to melt electronic order (4-6), drive insulator-to-metal transitions (7) and induce superconductivity (8). Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in Y[Ba.sub.2][Cu.sub.3][O.sub.6+x] (refs 9,10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state Y[Ba.sub.2][Cu.sub.3][O.sub.6+x] at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-[O.sub.2] intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O-Cu-O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] character of the in-plane electronic structure is likely to favour superconductivity., The response of a crystal lattice to strong, resonant excitation of an infrared-active phonon mode can be described by separating the crystal Hamiltonian into its linear and nonlinear terms: H [...]
- Published
- 2014