High-pressure study on structural instability in high-temperature superconductors

Miscellaneous · Fri Dec 31 00:00:00 EST 1993

OSTI ID:106828

Xiong, Quan

There may be a close correlation between high temperature superconductivity and various instabilities. Earlier studies of the A15 and related compounds show that the strong superconducting interaction in these compounds does significantly influence their structural, electronic, magnetic and stoichiometric properties, leading to the related instabilities. The partial or complete arrest of these instabilities in these compounds does raise T{sub c} slightly. Similar instabilities have also been detected in the cuprate high temperature superconductors (HTS`s). We have chosen to examine the structural instabilities in two representatives types of HTS`s, namely La{sub 2-x}A{sub x}CuO{sub 4} with A = Sr or Ba and RESr{sub 2}Cu{sub 2.7}Mo{sub 0.3}O{sub y} with RE = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb by the pressure effects. Interesting results have been obtained. We have observed that pressure affects the properties of the electronically similar La{sub 2-x}Sr{sub x}CuO{sub 4} and La{sub 2-x}Ba{sub x}CuO{sub 4} differently, particular near x = 0.12, where a low temperature tetragonal to low temperature orthorhombic (LLT-LTO) structural instability occurs. Previously reported anomalously large {alpha} in T{sub c} is not due to the isotope effect in its ordinary sense but with an electronic transition resulting from a Fermi-surface topology change. T{sub c} undergoes only a small and smooth change as the structure crosses the LTO to high temperature tetragonal phase boundary under pressure at x {approximately} 0.2. This suggests that HTS exists continuously from the orthorhombic to the tetragonal phase, in strong contrast to a recent proposition. By studying the superconducting and structural properties of the RESr{sub 2}Cu{sub 2.7}Mo{sub 0.3}O{sup 7} [RES(CM)O] compound system, we found that their dTc/dP is relatively large and similar to that for the REBa{sub 2}Cu{sub 3-x}X{sub x}O{sub 7} compound system.

• Research Organization: Houston Univ., TX (United States)
• OSTI ID: 106828
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: 1993
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
HIGH-TC SUPERCONDUCTORS
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
LANTHANUM OXIDES
COPPER OXIDES
STRONTIUM OXIDES
BARIUM OXIDES
SAMARIUM OXIDES
EUROPIUM OXIDES
GADOLINIUM OXIDES
TERBIUM OXIDES
DYSPROSIUM OXIDES
HOLMIUM OXIDES
THULIUM OXIDES
YTTERBIUM OXIDES
PRESSURE DEPENDENCE
SUPERCONDUCTIVITY
INSTABILITY
TRANSITION TEMPERATURE