Goldstone-Mode Phonon Dynamics in the Pyrochlore Cd₂Re₂O₇

Journal Article · Sat Jan 01 00:00:00 EST 2005 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.95.125503· OSTI ID:1003443

Kendziora, C. A. ^[1]; Sergienko, I. A. ^[2]; Jin, Rongying ^[3]; He, Jian ^[3]; Keppens, Veerle ^[3]; Sales, Brian C ^[3]; Mandrus, David ^[3]

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1. Naval Research Laboratory, Washington, D.C.
2. Memorial University of Newfoundland, St. John's Newfoundland, Canada
3. ORNL

We have measured the polarized Raman scattering spectra of Cd{sub 2}Re{sub 2}O{sub 7}, the first superconducting pyrochlore, as a function of temperature. For temperatures below the cubic-to-tetragonal structural phase transition (SPT) at 200 K, a peak with B{sub 1} symmetry develops at zero frequency with divergent intensity. We identify this peak as the first observation of the Goldstone phonon in a crystalline solid. The Goldstone phonon is a collective excitation that exists due to the breaking of the continuous symmetry with the SPT. Its emergence coincides with that of a Raman-active soft mode. The order parameter for both features derives from an unstable doubly degenerate vibration (with E{sub u} symmetry) of the O1 atoms which drives the SPT.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1003443
• Journal Information: Physical Review Letters, Vol. 95, Issue 12; ISSN 0031--9007
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ATOMS
COLLECTIVE EXCITATIONS
ORDER PARAMETERS
PHONONS
PYROCHLORE
SCATTERING
SPECTRA
SYMMETRY