Phonon dispersion and lattice dynamics of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">KTaO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>from 4 to 1220 K

Perry, C. H.; Currat, R.; Buhay, H.; Migoni, R. L.; Stirling, William; Axe, J. D.

doi:10.1103/physrevb.39.8666

Cited by 106 publications

(65 citation statements)

References 36 publications

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“…The importance of the p-d hybridization has been demonstrated for mixed crystals of KTa 1-x Nb x O 3 [29], where hyper Raman data could successfully be modeled within the polarizability model. The importance of that work for the following lies in the fact that for the understanding of the data a single quantity turned out to be the decisive one, namely the effective core-shell coupling K OB (T) [30]. This finding implies that only a limited number of parameters is relevant for the description of the dynamical and temperature dependent properties of ferroelectric perovskites.…”

Section: B) the Lattice Dynamical Modelmentioning

confidence: 99%

The polarizability model for ferroelectricity in perovskite oxides

Bussmann‐Holder

2012

J. Phys.: Condens. Matter

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This article reviews the polarizability model and its applications to ferroelectric perovskite oxides. The motivation for the introduction of the model is discussed and nonlinear oxygen ion polarizability effects and their lattice dynamical implementation outlined. While a large part of this work is dedicated to results obtained within the self-consistent-phonon approximation (SPA), also nonlinear solutions of the model are handled which are of interest to the physics of relaxor ferroelectrics, domain wall motions, incommensurate phase transitions. The main emphasis is to compare the results of the model with experimental data and to predict novel phenomena.

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Section: B) the Lattice Dynamical Modelmentioning

confidence: 99%

The polarizability model for ferroelectricity in perovskite oxides

Bussmann‐Holder

2012

J. Phys.: Condens. Matter

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“…The peaks at 4.92 and 7.33 THz are associated with TO 1,2 2 TA and TO 1,2 1 TA mode combinations, respectively, while the peak at 13.24 THz (16.7 THz) corresponds to the TO 4 2 TA (TO 4 1 TA) combination mode. The TO 2 branch dominates the TO 1,2 contributions because of its flatter dispersion associated with a high density of states along a large area of the D direction [10]. TA modes with lower q values and lower frequencies from the entire D direction are involved in the observed combinations therefore.…”

Section: (Received 15 November 1999)mentioning

confidence: 99%

“…It is associated with the generation of squeezed phonon states as shown by Garret et al [4,5,9]. All higher frequency peaks are identified as covariance oscillations of phonon amplitudes by comparison to the phonon dispersion curves [10] and the continuous-wave Raman spectra of KTaO 3 [6]. The peaks at 4.92 and 7.33 THz are associated with TO 1,2 2 TA and TO 1,2 1 TA mode combinations, respectively, while the peak at 13.24 THz (16.7 THz) corresponds to the TO 4 2 TA (TO 4 1 TA) combination mode.…”

Section: (Received 15 November 1999)mentioning

confidence: 99%

Impulsive Excitation of Phonon-Pair Combination States by Second-Order Raman Scattering

2000

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The excitation of (100)-oriented KTaO 3 with 25-fs laser pulses impulsively drives phonon-pair combination states via second-order Raman scattering. Oscillations in the phonon-amplitude covariance at the sum and difference frequency of the two involved phonons are observed in a spectrally and temporally resolved pump-probe experiment. Transmission changes of the sample are dominated by contributions of wave vector conserving phonon-pair combinations from the entire Brillouin zone that have maxima in their combined density of states. For low temperatures the temperature dependence of the covariance oscillations of different phonon combinations is reproduced by a quantum-mechanical model. PACS numbers: 78.47. + p, The investigation of coherent phonons in solids has been a field of extensive research since the first observation of coherent phonons in semiconductors [1]. Several excitation mechanisms for coherent lattice vibrations in solids have been identified until now [2]. In the framework of first-order impulsive stimulated Raman scattering coherent phonons are characterized by a nonzero expectation value of the phonon-amplitude oscillating with their eigenfrequency. The driving laser pulse reduces the uncertainty in the amplitudes and the canonical momenta. However, coherent states do not exhibit dynamics in statistic variables like amplitude variances and covariances of phonon modes. Different eigenmodes of the lattice remain uncorrelated.A route to induce macroscopically detectable dynamics in the statistical properties of the lattice is second-order Raman scattering (SOR). Recently, vacuum squeezing of phonons generated by SOR has been predicted by Hu and Nori [3] and demonstrated experimentally by Garret et al. in KTaO 3 [4]. They found that the uncertainties of the phonon amplitude and canonical momentum oscillate out of phase at twice the fundamental phonon frequency and temporarily drop below their vacuum noise level. KTaO 3 is ideally suited for studies on SOR, since for symmetry reasons it exhibits only second-order but no first-order Raman scattering. Thus the excitation of dynamics in the statistical properties of a solid such as amplitude variances (in general associated with squeezed states) and covariances of phonon-pair amplitudes (in general associated with correlations of phonon pairs) can be investigated directly. In this Letter we report on the observation of such combination states of phonon pairs generated by ultrashort light pulses via SOR in a solid: Two oscillators that are decoupled in the absence of perturbation (neglecting anharmonicities) become correlated.To model the second-order Raman excitation in KTaO 3 we consider two harmonic oscillators with amplitudes Q 1 , Q 2 and canonical momenta P 1 , P 2 coupled via the second-order polarizability a ij ≠ 2 a͞≠Q i ≠Q j by excitation with a linearly polarized optical pulse with electric field component E͑t͒. The unperturbed Hamiltonian H 0

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“…Information on the low frequency excitations in KTaO 3 , is available from scattering experiments such as, Raman [14], hyper-Raman [15,16], Brillouin [6,7,8], and neutron scattering [3,17,18,19,20], and from infrared spectroscopy [21,22]. Indirect information is also available from dielectric [23] and thermal [24] measurements.…”

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Low energy phonon spectrum and its parameterization in pure KTaO3 below 80 K

et al. 2000

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Abstract. High resolution data on low energy phonon branches (acoustic and soft optic) along the three principal symmetry axes in pure KTaO3 were obtained by cold neutron inelastic scattering between 10 and 80 K. Additional off-principal axis measurements were performed to characterize the dispersion anisotropy (away from the <100> and <110> axes). The parameters of the phenomenological model proposed by Vaks [28] are refined in order to successfully describe the experimental low temperature (10 < T < 100 K) dispersion curves, over an appreciable reciprocal space volume around the zone center (|q| < 0.25 rlu).The refined model, which involves only 4 temperature-independent adjustable parameters, is intended to serve as a basis for quantitative computations of multiphonon processes.

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Phonon dispersion and lattice dynamics ofKTaO3from 4 to 1220 K

Cited by 106 publications

References 36 publications

The polarizability model for ferroelectricity in perovskite oxides

The polarizability model for ferroelectricity in perovskite oxides

Impulsive Excitation of Phonon-Pair Combination States by Second-Order Raman Scattering

Low energy phonon spectrum and its parameterization in pure KTaO3 below 80 K

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