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Two-gap structure in Yb(Y)Ba2Cu3O7−x single crystals |
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| Authors: | B. A. Aminov M. A. Hein G. Müller H. Piel D. Wehler Ya. G. Ponomarev K. Rosner K. Winzer |
| Affiliation: | 1. Fachbereich Physik, Universit?t Wuppertal, D-42097, Germany 2. Physics Department, Moscow State University, Russia 3. 1 Physikalisches Institut, Physikalisches Universit?t G?ttingen, Germany |
| Abstract: | Tunneling effects in YbBa2Cu3O7?x (YbBCO) and YbBa2Cu3O7?x (YBCO) single crystals have been investigated using an improved technique of break junction preparation. A two-gap structure with BCS-like density of states has been observed. The value of the “large” gap is in the range of 24–28 meV for YBCO (T c =85–90 K) and 29–30 meV for YbBCO (T c =87–90 K). A variation of the value of the “small” gap between 0.5 and 11 meV has been detected, even for the same crystal. As a possible explanation, two-band superconductivity, surface properties, or strong gap anisotropy will be discussed. |
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