Phonon softening and anomalous mode near the xc =0.5 quantum critical point in Ca2-x Srx RuO4

R. G. Moore; M. D. Lumsden; M. B. Stone; Jiandi Zhang; Y. Chen; J. W. Lynn; R. Jin; D. Mandrus; E. W. Plummer

doi:10.1103/PhysRevB.79.172301

Phonon softening and anomalous mode near the xc =0.5 quantum critical point in Ca2-x Srx RuO4

R. G. Moore, M. D. Lumsden, M. B. Stone, Jiandi Zhang, Y. Chen, J. W. Lynn, R. Jin, D. Mandrus, E. W. Plummer

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Abstract

Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2-x Srx RuO4 (x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I 41 /acd structure as the temperature approaches the transition to a low-temperature orthorhombic (LTO) Pbca phase. This behavior is similar to that in La2 CuO4, 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 Σ4, albeit with similar dispersion. This anomalous phonon mode never softens below ∼5 meV, even for temperatures below the HTT-LTO transition. This mode is attributed to the presence of intrinsic structural disorder within the I 41 /acd tetragonal structure of the doped ruthenate.

Original language	English
Article number	172301
Journal	Physical Review B - Condensed Matter and Materials Physics
Volume	79
Issue number	17
DOIs	https://doi.org/10.1103/PhysRevB.79.172301
State	Published - May 1 2009

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title = "Phonon softening and anomalous mode near the xc =0.5 quantum critical point in Ca2-x Srx RuO4",

abstract = "Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2-x Srx RuO4 (x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I 41 /acd structure as the temperature approaches the transition to a low-temperature orthorhombic (LTO) Pbca phase. This behavior is similar to that in La2 CuO4, 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 Σ4, albeit with similar dispersion. This anomalous phonon mode never softens below ∼5 meV, even for temperatures below the HTT-LTO transition. This mode is attributed to the presence of intrinsic structural disorder within the I 41 /acd tetragonal structure of the doped ruthenate.",

author = "Moore, {R. G.} and Lumsden, {M. D.} and Stone, {M. B.} and Jiandi Zhang and Y. Chen and Lynn, {J. W.} and R. Jin and D. Mandrus and Plummer, {E. W.}",

year = "2009",

month = may,

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doi = "10.1103/PhysRevB.79.172301",

language = "English",

volume = "79",

journal = "Physical Review B - Condensed Matter and Materials Physics",

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T1 - Phonon softening and anomalous mode near the xc =0.5 quantum critical point in Ca2-x Srx RuO4

AU - Moore, R. G.

AU - Lumsden, M. D.

AU - Stone, M. B.

AU - Zhang, Jiandi

AU - Chen, Y.

AU - Lynn, J. W.

AU - Jin, R.

AU - Mandrus, D.

AU - Plummer, E. W.

PY - 2009/5/1

Y1 - 2009/5/1

N2 - Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2-x Srx RuO4 (x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I 41 /acd structure as the temperature approaches the transition to a low-temperature orthorhombic (LTO) Pbca phase. This behavior is similar to that in La2 CuO4, 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 Σ4, albeit with similar dispersion. This anomalous phonon mode never softens below ∼5 meV, even for temperatures below the HTT-LTO transition. This mode is attributed to the presence of intrinsic structural disorder within the I 41 /acd tetragonal structure of the doped ruthenate.

AB - Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2-x Srx RuO4 (x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I 41 /acd structure as the temperature approaches the transition to a low-temperature orthorhombic (LTO) Pbca phase. This behavior is similar to that in La2 CuO4, 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 Σ4, albeit with similar dispersion. This anomalous phonon mode never softens below ∼5 meV, even for temperatures below the HTT-LTO transition. This mode is attributed to the presence of intrinsic structural disorder within the I 41 /acd tetragonal structure of the doped ruthenate.

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U2 - 10.1103/PhysRevB.79.172301

DO - 10.1103/PhysRevB.79.172301

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VL - 79

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

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M1 - 172301

ER -

Phonon softening and anomalous mode near the xc =0.5 quantum critical point in Ca2-x Srx RuO4

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