Spectral weight changes at the superconducting transition of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8+. delta
- Stanford Univ., CA (United States). Stanford Electronics Labs.
- Los Alamos National Lab., NM (United States)
An overview of our gap studies in high-{Tc} superconductors is presented for the workshop on Fermiology of high-{Tc}'s. The work is centered on the study of single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. In a conventional BCS superconductor, a superconducting gap {Delta} is formed when the near Fermi edge electrons condense to form Cooper pairs at low temperatures. As the material goes superconducting the density of states is modified such that the spectral intensity in the region from the Fermi energy down to an energy {Delta} is transferred to a regions just below {Delta}. While this spectral weight transfer has in the past been studied with tunneling spectroscopy, the size of the gap as well as improvements in our instrument resolution allow us now to study it with photoelectron spectroscopy. We have found that as the sample goes superconducting, not only is there spectral weight transfer from the gap region as in BCS theory, but along the {Gamma}-M direction there is also some spectral weight transfer from higher binding energies resulting in a dspectral dip at about {minus}90 meV relative E{sub F}. The total spectral weight decreases along the {Gamma}-M direction, but actually increases along the {Gamma}-X direction. This temperature dependent spectral transfer is discussed in terms of (1) a two to three dimensional phase transition from RVB theory; (2) a manifestation of the electron-boson interaction in the form of {alpha}{sup 2}F oscillations; and (3) conformity with the theory of Van Hove singularities. The latter are particularly attractive in that there are several other observations possibly explained by them: (1) the observation that the magnitude of the gap is anisotropic in the a-b plane; (2) the observation that for overdoped samples the magnitude of D appears to fall off faster then {Tc}. 25 refs., 8 figs., 1 tab.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); National Science Foundation, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5124161
- Report Number(s):
- LA-UR-91-3223; CONF-9103112-6; ON: DE92002455; CNN: DMR-8913478; DAAG29-85-K-0048; N00014-87-K-0327
- Resource Relation:
- Conference: Conference on fermiology of high T sub c superconductors, Argonne, IL (United States), 25-27 Mar 1991
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BISMUTH OXIDES
ELECTRONIC STRUCTURE
CALCIUM OXIDES
COPPER OXIDES
STRONTIUM OXIDES
CRYSTALS
ENERGY LEVELS
FERMI LEVEL
HIGH-TC SUPERCONDUCTORS
PHOTOEMISSION
SPECTROSCOPY
TRANSITION TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
EMISSION
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SECONDARY EMISSION
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
640302 - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory
656100 - Condensed Matter Physics- Superconductivity