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Evidence for pseudogap and phase-coherence gap separation by Andreev reflection experiments in Au/ La 2 - x Sr x CuO 4 point-contact junctions |
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| Authors: | RS Gonnelli A Calzolari D Daghero L Natale GA Ummarino VA Stepanov M Ferretti |
| Institution: | (1) INFM - Dipartimento di Fisica, Politecnico di Torino, 10129 Torino, Italy, IT;(2) P.N. Lebedev Physical Institute, Russian Academy of Sciences, 117924 Moscow, Russia, RU;(3) Dipartimento di Chimica e Chimica Industriale, Università di Genova, 16146 Genova, Italy, IT |
| Abstract: | We present new Au/La2-xSrxCuO4 (LSCO) point-contact conductance measures as a function of voltage and temperature in samples with 0.08 ? x ? 0.2. Andreev reflection features disappear at about the bulk T c , giving no evidence of gap for T > T c . The fit of the normalized conductance at any T < T c supports a (s + d)-wave symmetry of the gap, whose dominant low-T s component follows the T c ( x ) curve in contrast with recent angle-resolved photoemission spectroscopy and quasiparticle tunneling data. These results prove the separation between pseudogap and phase-coherence superconducting gap in LSCO at x 0.2. Received 14 June 2001 |
| Keywords: | PACS 74 50 +r Proximity effects weak links tunneling phenomena and Josephson effects – 74 25 Dw Superconductivity phase diagrams – 74 72 Dn La-based cuprates |
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