Lattice vibrations in KCuF<sub>3</sub>

Schmidt, Michael; Wang, Zhe; Kant, Ch.; Mayr, F.; Schrettle, F.; Nidda, H.-A. Krug von; Ghigna, Paolo; Tsurkan, V.; Loidl, A.

doi:10.1002/andp.201100026

Cited by 5 publications

(7 citation statements)

References 39 publications

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“…Figure 7 shows the temperature evolution of the heat capacity divided by temperature (C/T ) for the I4/mcm and P 4/mbm polymorphs. The calculated C/T remains in close agreement with the results of the measurements reported by Deisenhofer et al [10]. It should be noted that the experimental heat capacity contains also the magnetic contribution, and thus a typical λ-type behavior is expected in the vicinity of the respective Néel temperatures (39 K and 23 K).…”

Section: Resultssupporting

confidence: 89%

“…This feature was assigned to a splitting of the doubly degenerated E u mode. The IR phonon of A 2u symmetry at ∼250 cm −1 also exhibits some anomalous behavior below 150 K, which was related to the multiphonon processes [10]. Such a deviation is not observed neither for the calculated E u nor A 2u mode.…”

Section: Resultsmentioning

confidence: 81%

“…It was suggested, that this low-frequency mode can be either magnetic in its origin or it may correspond to a phonon mode of the orthorhombic structure. On one hand, a possible orthorhombic structure [11] would show three IR-active modes of B 1 and B 3 symmetries in the very close vicinity of the mode at 107 cm −1 , but on the other hand, its IR-spectrum would exhibit much finer structure than that reported in [10]. In general, the total number of the IR-active phonons of B 1 , B 2 , and B 3 symmetries in the orthorhombic phase with the P 2 1 2 1 2 1 space group amounts to 90.…”

Section: Resultsmentioning

confidence: 86%

“…Calculated (circles) and experimental[7] (squares) Raman active modes in the I4/mcm (a-type) and P 4/mbm (d-type) polymorphs of KCuF 3 . Calculated and experimental[10] IR-active modes in the I4/mcm (a-type) and P 4/mbm (d-type) polymorphs of KCuF 3 . Frequencies of TO and LO modes are indicated by solid and open symbols, respectively.…”

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confidence: 99%

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Vibrational properties and the stability of the KCuF₃phases

Legut¹,

Wdowik²

2013

J. Phys.: Condens. Matter

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We report theoretical investigations of the lattice dynamics of KCuF(3). Our calculations are based on the generalized gradient approximation and parametrization of Perdew-Burke-Ernzerhof to the density functional theory corrected for on-site Coulomb interaction (GGA + U). Vibrations of the KCuF(3) lattice are studied within the harmonic approximation. Energetic stability of tetragonal and orthorhombic polymorphic structures of KCuF(3) is analyzed. Our results show that the orthorhombic polymorph is energetically not preferred. The Raman and infrared-active phonon modes in two distinct tetragonal polymorphs of KCuF(3) are discussed with respect to the available experimental data. A detailed examination of the phonon densities of states in both tetragonal polymorphic structures of KCuF(3) is provided together with discussion on similarities and differences between the vibrational dynamics of two distinct tetragonal lattices of the KCuF(3) system.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 86%

mentioning

confidence: 99%

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Vibrational properties and the stability of the KCuF₃phases

Legut¹,

Wdowik²

2013

J. Phys.: Condens. Matter

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“…Far below T OO , a new, dynamic, phase appears to manifest itself. The work of Deisenhofer et al [5] reports a splitting of the infraredactive phonon mode E u (3) at ∼ 150 K, indication of symmetry lowering; an analogous splitting of the E g (2) mode is seen in Raman scattering slightly above the Neel temperature, T N = 40 K. This makes KCuF 3 remarkable in yet another way -as a compound whose low temperature properties are dominated by dynamics. Indeed, the evolution of the E g (2) and E u (3) modes with temperature could be understood if strong lattice fluctuations around a lower symmetry orthorhombic lattice were present.…”

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confidence: 92%

Lattice distortions in KCuF3: a paradigm shift?

Pavarini

2011

Ann. Phys.

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KCuF 3 is the paradigmatic compound for the co-operative Jahn-Teller effect. But do we really know its structure?Co-operative Jahn-Teller distortions are ubiquitous. But do we really know where they come from? Usually they go along with other distortions and ordering phenomena, which make it difficult to identify the actual driving mechanism. KCuF 3 is believed to be a beautiful exception, the cleanest realization of a co-operative Jahn-Teller system. Its CuF 6 octahedra are slightly compressed along z, and have a long (l) and a short (s) CuF bond in the xy plane. The electronic configuration of Cu is 3d9 , a single hole in the e g states; the distortions split the otherwise degenerate e g orbitals, and the hole goes into the |s 2 -z 2 state. The spatial alternation of l and s bonds in all direction produces the orbital pattern shown in Fig. 1. Despite its simple structure, the origin of the co-operative Jahn-Teller distortion in KCuF 3 remained a puzzle. Is it driven by electron-phonon coupling or by many-body superexchange [1]? Early-on static mean-field LDA+U calculations showed that the stability of the Jahn-Teller distortion (total energy gain) is strongly enhanced by Coulomb repulsion, a result recently confirmed by dynamical mean-field (DMFT) calculations [2]. Does this mean that many-body super-exchange is driving the co-operative distortion? The answer remained elusive for half a century. Only recently, by using DMFT and a new approach to separate super-exchange and electron-phonon coupling effects, the puzzle was finally solved. It was shown [3,4] that many-body super-exchange alone gives a critical temperature of about 350 K, very large, but far too low to explain experimental facts: the co-operative Jahn-Teller distortion persists up to T OO ∼ 800 K, and probably at even higher temperatures. Hence the static Jahn-Teller distortions must be driven by electronphonon coupling. *

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Robustness of Spin-Chain State-Transfer Schemes

Stolze

Álvarez

Osenda

et al. 2013

Quantum State Transfer and Network Engineering

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This is a shortened and slightly edited version of a chapter [1] in the collection Quantum State Transfer and Network Engineering, edited by G.M. Nikolopoulos and I. Jex [2], where we review our own research about the robustness of spin-chain state-transfer schemes along with other approaches to the topic. Since our own research is documented elsewhere to a large extent we here restrict ourselves to a review of other approaches which might be useful to other researchers in the field.

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Lattice vibrations in KCuF₃

Cited by 5 publications

References 39 publications

Vibrational properties and the stability of the KCuF₃phases

Vibrational properties and the stability of the KCuF₃phases

Lattice distortions in KCuF3: a paradigm shift?

Robustness of Spin-Chain State-Transfer Schemes

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Lattice vibrations in KCuF3

Cited by 5 publications

References 39 publications

Vibrational properties and the stability of the KCuF3phases

Vibrational properties and the stability of the KCuF3phases

Lattice distortions in KCuF3: a paradigm shift?

Robustness of Spin-Chain State-Transfer Schemes

Contact Info

Product

Resources

About

Lattice vibrations in KCuF₃

Vibrational properties and the stability of the KCuF₃phases

Vibrational properties and the stability of the KCuF₃phases