Publications by Andrea Cavalleri

Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>6.5</inf>

Nature 516 (2014) 71-73

R Mankowsky, A Subedi, M Först, SO Mariager, M Chollet, HT Lemke, JS Robinson, JM Glownia, MP Minitti, A Frano, M Fechner, NA Spaldin, T Loew, B Keimer, A Georges, A Cavalleri

© 2014 Macmillan Publishers Limited. All rights reserved.Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures1-3. In complex oxides, this method has been used to melt electronic order4-6, drive insulator-to-metal transitions7 and induce superconductivity8. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+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 YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-O2 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 dx2-y2 character of the in-plane electronic structure is likely to favour superconductivity.

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