Phonon softening and anomalous mode near the xc=0.5 quantum critical point in Ca2-xSrxRuO4

Journal Article · Thu Jan 01 00:00:00 EST 2009 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.79.172301· OSTI ID:964353

Moore, R. G. ^[1]; Lumsden, Mark D ^[2]; Stone, Matthew B ^[2]; Zhang, Jiandi ^[3]; Chen, Y. ^[4]; Lynn, J. W. ^[4]; Jin, Rongying ^[2]; Mandrus, David ^[2]; Plummer, E. W. ^[1]

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1. University of Tennessee, Knoxville (UTK)
2. ORNL
3. Florida International University, Miami
4. National Institute of Standards and Technology (NIST)

Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca{sub 2-x}Sr{sub x}RuO{sub 4} (x = 0.4,0.6). The in-plane {Sigma}{sub 4} octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I4{sub 1}/acd structure as the temperature approaches the transition to a low-temperature orthorhombic (LTO) Pbca phase. This behavior is similar to that in La{sub 2}CuO{sub 4}, but an inelastic feature that is not found in the cuprate is present. An anomalous phonon mode is observed at energy transfers greater than the {Sigma}{sub 4}, albeit with similar dispersion. This anomalous phonon mode never softens below {approx} 5 meV, even for temperatures below the HTT-LTO transition. This mode is attributed to the presence of intrinsic structural disorder within the I4{sub 1}/acd tetragonal structure of the doped ruthenate.

• 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: 964353
• Journal Information: Physical Review B, Vol. 79, Issue 17; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CUPRATES
ENERGY TRANSFER
NEUTRONS
PHONONS
SCATTERING