Lattice dynamics and the electron-phonon interaction in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>Ca</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>RuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>

Rho, Heesuk; Cooper, S. L.; Nakatsuji, Satoru; Fukazawa, H.; Maeno, Y.

doi:10.1103/physrevb.71.245121

Cited by 20 publications

(23 citation statements)

References 41 publications

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“…The increased asymmetry in the insulating paramagnetic state is in qualitative agreement with Ref. 24. The dark blue star marks the asymmetry value for Sr-doped Ca2RuO4 at 456 cm −1 (B1g channel), taken from Ref.…”

supporting

confidence: 88%

“…The phonon asymmetry can be obtained from fits to a Fano profile: I(ν) = I 0 (q + ) 2 /(1 + ) 2 , with = (ν − ν p )/Γ. Besides the phonon frequency ν p and the effective phonon linewidth Γ, we extract the Fano parameter q whose inverse is directly proportional to the electron-phonon coupling strength and the imaginary part of the electronic susceptibility 24,34 . In Fig.…”

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confidence: 99%

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Raman scattering from current-stabilized nonequilibrium phases in Ca2RuO4

et al. 2019

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We used Raman light scattering to study the current-stabilized nonequilibrium semimetallic and metallic phases in Ca2RuO4. By determining the local temperature through careful analysis of the Stokes and anti-Stokes intensities, we find that Joule heating can be completely avoided by supplying sufficient cooling power in a helium-flow cryostat, and that the current induces the semimetallic state without inducing any significant heating. We further investigate the current-induced semimetallic state as a function of temperature and current. We confirm the absence of long-range antiferromagnetic order and identify a substantial Fano broadening of several phonons, which suggests coupling to charge and orbital fluctuations. Our results demonstrate that the semimetallic state is a genuine effect of the applied electrical current and that the current-induced phases have characteristics distinct from the equilibrium ones.Controlling and stabilizing electronic phases in correlated-electron materials are pivotal objectives of modern solid-state science 1,2 . In this context, compounds with 4d valence electrons have attracted a lot of attention as a plethora of ground states can be observed 3 . In particular, the fine balance between electron correlations, spin-orbit coupling and structural distortions in 4d metal oxides manifests itself as a high susceptibility to external perturbations. One prominent example is the layered perovskite system (Ca 1−x Sr x ) 2 RuO 4 whose end members, Ca 2 RuO 4 and Sr 2 RuO 4 , are a Mott insulator and an unconventional superconductor, respectively 4,5 .Ca 2 RuO 4 shows a temperature-driven insulator-tometal transition (IMT) at T IMT = 357 K 6-8 . The concomitant structural phase transition preserves the lattice symmetry (space group Pbca), but yields elongated RuO 6 octahedra with a reduced tilt and an enlarged c lattice parameter in the high-temperature metallic state. The insulating and metallic phases are therefore named "S"-Pbca and "L"-Pbca phase, respectively, where S and L refer to short and long c axes. In addition to temperature, other parameters, such as Sr substitution 5 , epitaxial strain 9 and hydrostatic pressure 10 , can turn Ca 2 RuO 4 metallic.The key role of octahedral rotation, compression and tilts is further exemplified in the magnetic state of Ca 2 RuO 4 , which sets in at T N = 110 K and is characterized by an A-type antiferromagnetic (AFM) ordering 6 . Several theoretical 11-13 and experimental 14,15 studies point towards an unconventional mechanism for magnetic ordering in Ca 2 RuO 4 , resulting from the condensation of spin-orbit excitons. The "excitonic magnetism" model further predicts that Ca 2 RuO 4 lies close to a quantum critical point separating antiferromagnetic and spin-orbit singlet states, which was confirmed by the experimental observation of a soft longitudinal amplitude mode of the spin-orbit condensate.Recent research has revealed new perspectives for insitu control of nonequilibrium phases in Ca 2 RuO 4 by electrical currents. In their pioneering wo...

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mentioning

confidence: 99%

Raman scattering from current-stabilized nonequilibrium phases in Ca2RuO4

et al. 2019

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“…The electron-phonon coupling constant V shows a comparable increase by 13% with decreasing temperature to 10 K, but, instead of softening, the B 1g mode hardens, similarly to all other Sr 3 Ru 2 O 7 modes. 14 A mode softening due to the opening of a charge gap is also not consistent with the results of Rho et al, 15 who observed strong hardening below T M of the Fano-shaped B 1g line at Ϸ430 cm −1 , in closely related Ca 2−x Sr x RuO 4 . Finally, the recent magnetic field-dependent Raman measurements on Ca 3 Ru 2 O 7 of Karpus et al 9 have shown that the anomalous shift of the 435/ 413 cm −1 phonon can be reversed with a magnetic field along the a axis.…”

Section: B Phonon and Electron Scattering Anomalies Near T Mmentioning

confidence: 39%

Raman spectroscopy ofCa3Ru2O7: Phonon line assignment and electron scattering

et al. 2005

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The polarized Raman spectra of layered ruthenate Ca 3 Ru 2 O 7 were measured between 5 and 300 K in several exact scattering configurations. All observed Raman lines were assigned to definite phonon modes of A 1 or A 2 symmetry on the basis of their polarization properties and by comparison to the results of lattice dynamical calculations for the orthorhombic A2 1 ma structure. It is established that the Fano-shaped A 2 mode, which exhibits a strong anomaly near the metal-nonmetal transition at T M = 48 K, involves mainly in-plane breathingtype oxygen vibrations. Other A 2 modes also exhibit detectable anomalies near T M . We argue that the phonon softening below T M is largely due to the orbital ordering and related structural changes.

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“…[21][22][23][24][25] Therefore, by carefully monitoring the inverse asymmetry parameters as a function of temperature, one can obtain useful information regarding the evolution of the electronic density of states and the electronphonon coupling in ͑Bi, Pb͒-Sr-Co-O. Illustrated by plotting the asymmetry parameter as a function of temperature, the evolution of the electron-phonon coupling is shown in Fig.…”

Section: Raman Tensormentioning

confidence: 99%

Raman-scattering study of misfit-layered (Bi, Pb)-Sr-Co-O single crystal

Yuan

et al. 2007

Journal of Applied Physics

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Polarized Raman scattering measurements were performed on misfit-layered thermoelectric Bi2−xPbxSr2Co2Oy(x=0.6) single crystal from 20 K to room temperature. Four peaks were observed in the parallel polarization channel and no peaks in the cross polarization channel. One of the Raman peaks carries the asymmetric characteristic, which can be regarded as an evidence of the existence of electron-phonon coupling. Furthermore, the asymmetric parameter, proportional to the strength of electron-phonon coupling, was estimated with the asymmetric Breit–Wigner–Fano line shape. The electron-phonon coupling may play an important role in understanding the large thermoelectric power of cobalt based materials.

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Lattice dynamics and the electron-phonon interaction inCa2RuO4

Cited by 20 publications

References 41 publications

Raman scattering from current-stabilized nonequilibrium phases in Ca2RuO4

Raman scattering from current-stabilized nonequilibrium phases in Ca2RuO4

Raman spectroscopy ofCa3Ru2O7: Phonon line assignment and electron scattering

Raman-scattering study of misfit-layered (Bi, Pb)-Sr-Co-O single crystal

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