Gap and sub-gap structures of intrinsic Josephson tunnel junctions in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} single crystals

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:548487

Yurgens, A; Winkler, D; Zavaritsky, N; Claeson, T ^[1]

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1. Chalmers Univ. of Technology, Goeteborg (Sweden)

Stacked series arrays of intrinsic Josephson (IJ) tunnel junctions fabricated on the surfaces of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} (BI2212) single crystals by photolithography have been studied. Advanced technology with in-situ control of stack heights allows one to make a specified number (3--200) of junctions in the stack. The quasi-particle branch of an individual IJ junction has a well-developed gap structure. The gap value is {approximately} 12--13 meV at low temperature, which is approximately two times smaller than reported elsewhere. The temperature dependence of the gap deviates strongly from the BCS one. Proximity induced superconductivity of the Bi-O layers is one probable explanation for the reduced gap observed in the experiments. True superconducting contact obtained between the outermost Bi-O layer of a freshly cleaved Bi2212 single crystal and a Pb thin film is a supporting evidence for the Bi-O layers being superconducting. Multiple peaks are seen in the first derivative of the current-voltage characteristics at sub-gap voltages for all samples studied. The peak positions in voltage do not change with temperature and do not depend on the dimensions of the stack. Dynamic modulation of the tunnel density of states by low energy optical phonons and/or resonant tunneling through localized electronic states of the Bi-O and Sr-O layers are possible reasons for these observations.

• Sponsoring Organization: International Science Foundation
• OSTI ID: 548487
• Report Number(s): CONF-960163--; ISBN 0-8194-2071-9
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
BISMUTH OXIDES
CALCIUM OXIDES
COPPER OXIDES
ENERGY GAP
FABRICATION
HIGH-TC SUPERCONDUCTORS
JOSEPHSON JUNCTIONS
PROXIMITY EFFECT
STRONTIUM OXIDES
SUPERCONDUCTIVITY