Point contact tunneling study of the high transition temperature superconductor Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8

Conference · Wed Apr 01 00:00:00 EST 1992 · AIP Conference Proceedings (American Institute of Physics); (United States)

OSTI ID:7207216

Jiang, M H; Ventrice, C A; Scoles, K J; Tyagi, S; DiNardo, N J; Rothwarf, A ^[1]

---

1. 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-31-109-ENG-38
• OSTI ID: 7207216
• Report Number(s): CONF-9109102-; CODEN: APCPC
• Journal Information: AIP Conference Proceedings (American Institute of Physics); (United States), Vol. 251:1; Conference: 5. annual conference on superconductivity and applications, Buffalo, NY (United States), 24-26 Sep 1991; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BISMUTH OXIDES
TUNNEL EFFECT
CALCIUM OXIDES
COPPER OXIDES
STRONTIUM OXIDES
ELECTRIC CONTACTS
ELECTRIC CURRENTS
ENERGY GAP
HIGH-TC SUPERCONDUCTORS
MONOCRYSTALS
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTALS
CURRENTS
ELECTRICAL EQUIPMENT
EQUIPMENT
OXIDES
OXYGEN COMPOUNDS
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)