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  Först, M.; Frano, A.; Kaiser, S.; Mankowsky, R.; Hunt, C.; Turner, J.; Dakovski, G.; Minitti, M.; Robinson, J.; Loew, T.; Le Tacon, M.; Keimer, B.; Hill, J.; Cavalleri, A.; Dhesi, S.: Femtosecond x rays link melting of charge-density wave correlations and light-enhanced coherent transport in YBa₂Cu₃O_6.6. Physical Review B 90 (2014), p. 184514/1-4

10.1103/PhysRevB.90.184514
Open Access Version

Abstract:
We use femtosecond resonant soft x-ray diffraction to measure the optically stimulated ultrafast changes of charge-density wave correlations in underdoped YBa2Cu3O6.6. We find that when coherent interlayer transport is enhanced by optical excitation of the apical oxygen distortions, at least 50% of the in-plane charge-density wave order is melted. These results indicate that charge ordering and superconductivity may be competing up to the charge ordering transition temperature, with the latter becoming a hidden phase that is accessible only by nonlinear phonon excitation.