Anisotropic photoexcited carrier dynamics in (100)-, (001)-, and (110)-oriented YBCO films by polarized ultrafast optical spectroscopy

We report the time-resolved ultrafast optical spectroscopy results obtained from a series of well characterized (001)-, (100)- and (110)-oriented YBa₂Cu₃O₇-δ (YBCO) superconducting films prepared by pulsed laser deposition. The well-controlled film orientation has allowed us to probe the relaxation dynamics along various crystal orientations using respectively polarized pump and probe laser beams. The significant anisotropies in both the magnitude of the characteristic relaxation time and the temperature dependence of the photo-induced transient reflectance change indicate the nature of relaxation channel might be intrinsically different along different orientations. The implications of the results on the fundamental characteristics concerning superconducting gaps are discussed.