Regensburg 2004 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

TT: Tiefe Temperaturen

TT 8: Postersitzung I: Supraleitung

TT 8.3: Poster

Monday, March 8, 2004, 14:30–19:00, Poster A

Novel consideration of the phase diagram of electron doped high-temperature superductors — •Yoshiharu Krockenberger¹, Michio Naito¹, Akio Tsukada¹, Hideki Yamamoto¹, Lambert Alff², and Rudolf Gross² — ¹NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan — ²Walther-Meissner-Institut, 85748 Garching, Germany

The common phase diagram of high-temperature superconductors (HTS) including electron doped HTS was published first by Luke et al.[1]. Improved sample quality of hole doped cuprates supported and extended this phase diagram. Using molecular beam epitaxy it is possible to grow high quality single phase thin films of electron doped high-temperature superconductors. Usually, for doping the T^′-structure tetravalent Ce (e.g. La_2−xCe_xCuO_4+δ) is used. Using trivalent ions instead of Ce⁴⁺, e.g. Tb³⁺, one would expect a Mott insulating and antiferromagnetic state. The c-axis dependence of the doping level as well as XPS measurements clearly show that the Tb-cation is in the trivalent state. Furthermore, other trivalent dopants such as Lu, Y, Dy, Eu, and Sm have been investigated and all of them show the same result: superconductivity below about 20 K. This result may shed new light on the usually used phase diagram of electron doped high temperature superconductors.

[1] G. M. Luke et al., Phys. Rev. B 42, 7981 (1990)