Susceptibility and Knight-shift anomalies in cuprate superconductors

Journal Article · Thu Jun 01 04:00:00 EDT 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.51.15393· OSTI ID:54944

Thoma, J; Tewari, S; Ruvalds, J ^[1]; Rieck, C T ^[2]

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1. Physics Department, University of Virginia, Charlottesville, Virginia 22903 (United States)
2. Abteilung fuer Theoretische Festkoerperphysik, Universitaet Hamburg, Hamburg (Germany)

The unconventional temperature variation of the static susceptibility {chi}({ital T}) that has been discovered in various copper oxide superconductors is explained in terms of a model density of states that has a step shape at an energy threshold {ital E}{sub 0} along with a logarithmic Van Hove singularity at the same {ital E}{sub 0}. Calculations of {chi}({ital T}) and the Knight shift above the superconducting transition temperature {ital T}{sub {ital c}} yield good fits to the YBCO, BSCCO, and LSCO data by adjusting only the Fermi energy {mu} in correspondence to the oxygen or Sr content, respectively. When {mu} is right on or slightly below the Van Hove singularity, an upturn in {chi} occurs as the temperature {ital T} is lowered. By contrast, when {mu} is slightly above the threshold energy {ital E}{sub 0}, a downturn in {chi} is achieved as {ital T} is lowered. A correlation of these phenomena with experimental data provides insight into the proximity of the Van Hove singularity to {mu} in several cuprate superconductors. The YBCO and TBCO cuprates with the higher {ital T}{sub {ital c}} values exhibit a nearly constant susceptibility that suggests a Fermi energy well removed from the Van Hove singularity. The sensitivity of {ital T}{sub {ital c}} as well as the susceptibility to chemical changes may provide tests of electronic mechanisms of electron pairing as well as the BCS theory.

• OSTI ID: 54944
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 21 Vol. 51; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ENERGY-LEVEL DENSITY
FERMI LEVEL
HIGH-TC SUPERCONDUCTORS
KNIGHT SHIFT
MAGNETIC SUSCEPTIBILITY
TEMPERATURE DEPENDENCE
TRANSITION TEMPERATURE