Point contact tunneling study of the high transition temperature superconductor Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8
- Ben Franklin Superconductivity Center, and Drexel University, Philadelphia, PA 19104 (United States)
The point-contact (Pt-Ir probe) tunneling measurements on high-{ital T}{sub {ital c}} superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals ({ital T}{sub {ital c}}=82{degree} K) have been performed from 4.2 K to 77 K. A high conductance region around the origin, which is attributed to the junction of the pure metallic-bridge type of point-contact tunneling, has been observed. There are also several current steps beyond the high conductance region in the I-V curves, corresponding to conductance troughs, which are either zero or negative, in the dI/dV characteristics of the tunneling spectra. These are pronounced structures indicative of bound states in tunneling spectroscopy. A superconducting energy gap of {Delta}=26{plus minus}2 meV has been identified from tunneling spectra taken at {ital T}=4.2 K and as a function of temperature. Current drops with some regularity in voltage intervals between drops, occur at high applied voltage ({gt}80 mV). This resonance tunneling is the result of the effects of quantization due to the layered-structure of the crystal. A model based on the superlattice-like nature of the crystal has been developed to interpret the tunneling observation of the bound states and the energy gap. When a normal-metal probe is brought into contact with the superconducting crystal, the region of the first CaCuO slab under that contact will be most likely reduced to a low {ital T}{sub {ital c}} region with a smaller energy gap {Delta}{sub 1}, or even completely reduced to the normal state, due to the work function difference between the normal metal and the superconductor and/or the proximity effect. However, the second CaCuO slab remains in the intrinsic superconducting state with energy gap {Delta}{sub 2}{gt}{Delta}{sub 1}.
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 7207216
- Report Number(s):
- CONF-9109102--
- Journal Information:
- AIP Conference Proceedings (American Institute of Physics); (United States), Journal Name: AIP Conference Proceedings (American Institute of Physics); (United States) Vol. 251:1; ISSN 0094-243X; ISSN APCPC
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTALS
CURRENTS
ELECTRIC CONTACTS
ELECTRIC CURRENTS
ELECTRICAL EQUIPMENT
ENERGY GAP
EQUIPMENT
HIGH-TC SUPERCONDUCTORS
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TRANSITION ELEMENT COMPOUNDS
TUNNEL EFFECT