Doping Dependence of Two Energy Scales in the Tunneling Spectra of Superconducting La_<2-x>Sr_xCuO_4(Condensed matter : electronic structure and electrical, magnetic, and optical properties)

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Scanning tunneling microscopy and spectroscopy have been performed on superconducting La_<2-x>Sr_xCuO_4 (x = 0.06, 0.12, 0.16, and 0.21) at 4.2 K. Atomically resolved surface topography has been observed on the ab surface, which exhibits a one-dimensional structure corresponding to the buckling pattern of the orthorhombic phase. The tunneling spectra of all samples exhibit kinks at about ±5 meV in addition to the energy gap, indicating the existence of two energy scales. While the gap magnitude varies on the length scale of a few nm and steadily increases upon underdoping, the kink energy is spatially uniform on the surface and almost independent of the doping level.
社団法人日本物理学会の論文
2008-05-15