Percolation model for long wave phonons in random zincblende alloys: from II‐VI's to III‐V's

Chafi, A.; Pagès, O.; Fristot, Danièle; Postnikov, A. V.; Tite, Teddy; Laurenti, J.P.; Bormann, D.; Maksimov, O.; Tamargo, M. C.

doi:10.1002/pssc.200564730

Cited by 3 publications

(7 citation statements)

References 11 publications

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“…(a) Composition dependence of the Zn 1−x Be x Te TO branches (plain lines) schematically derived from Raman frequencies obtained with epitaxial layers (available in Refs. 26 – 28 ). The current data obtained with bulk crystals are superimposed (triangles), for comparison.…”

Section: Introductionmentioning

confidence: 99%

Exceptional phonon point versus free phonon coupling in Zn1−xBexTe under pressure: an experimental and ab initio Raman study

Shoker

Alhaddad

Pagès

et al. 2022

Sci Rep

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Raman scattering and ab initio Raman/phonon calculations, supported by X-ray diffraction, are combined to study the vibrational properties of Zn1−xBexTe under pressure. The dependence of the Be–Te (distinct) and Zn–Te (compact) Raman doublets that distinguish between Be- and Zn-like environments is examined within the percolation model with special attention to x ~ (0,1). The Be-like environment hardens faster than the Zn-like one under pressure, resulting in the two sub-modes per doublet getting closer and mechanically coupled. When a bond is so dominant that it forms a matrix-like continuum, its two submodes freely couple on crossing at the resonance, with an effective transfer of oscillator strength. Post resonance the two submodes stabilize into an inverted doublet shifted in block under pressure. When a bond achieves lower content and merely self-connects via (finite/infinite) treelike chains, the coupling is undermined by overdamping of the in-chain stretching until a «phonon exceptional point» is reached at the resonance. Only the out-of-chain vibrations «survive» the resonance, the in-chain ones are «killed». This picture is not bond-related, and hence presumably generic to mixed crystals of the closing-type under pressure (dominant over the opening-type), indicating a key role of the mesostructure in the pressure dependence of phonons in mixed crystals.

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Section: Introductionmentioning

confidence: 99%

Exceptional phonon point versus free phonon coupling in Zn1−xBexTe under pressure: an experimental and ab initio Raman study

Shoker

Alhaddad

Pagès

et al. 2022

Sci Rep

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“…An upper estimate of the coupling frequency 𝜔 ′ = √𝑘′ 𝜇 ⁄along the procedure used with Zn1-xBexSe 10 (supplementary information -Fig. S7)is ~50 cm -1 , i.e., roughly one order of magnitude less than the TO frequency of pure BeTe [26][27][28] , i.e., 𝜔 0 ~461 cm -1 . As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…A schematic overview of the 1-bond→2-mode percolation-type Raman pattern of Zn1-xBexTe at ambient pressure (plain lines), based on the transverse optic (TO) modes earlier detected with epitaxial layers [26][27][28] , is displayed in Fig. 1a, for reference pupose.…”

Section: Resultsmentioning

confidence: 99%

“…(a) Composition dependence of the Zn1-xBexTe TO branches (plain lines) schematically derived from Raman frequencies obtained with epitaxial layers (available in Refs. [26][27][28]. The current data obtained with bulk crystals are superimposed (triangles), for comparison.…”

Section: Figure Captionsmentioning

confidence: 99%

“…Figure 1  Zn1-xBexTe Percolation scheme at ambient pressure. (a) Composition dependence of the Zn1-xBexTe TO branches (plain lines) schematically derived from Raman frequencies obtained with epitaxial layers (available in Refs [26][27][28]…”

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Exceptional Phonon Point Versus Free Phonon Coupling in Zn1-xBexTe Under Pressure: An Experimental and ab Initio Raman Study

Shoker

Alhaddad

Pagès

et al. 2021

Preprint

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Raman scattering and ab initio Raman/phonon calculations, supported by X-ray diffraction, are combined to study the vibrational properties of Zn1-xBexTe under pressure. The dependence of the Be-Te (distinct) and Zn-Te (compact) Raman doublets that distinguish between Be- and Zn-like environments is examined within the percolation model with special attention to x~(0,1). The Be-like environment hardens faster than the Zn-like one under pressure, resulting in the two sub-modes per doublet getting closer and mechanically coupled. When a bond is so dominant that it forms a matrix-like continuum, its two submodes freely couple on crossing at the resonance, with an effective transfer of oscillator strength. Post resonance the two submodes stabilize into an inverted doublet shifted in block under pressure. When a bond achieves lower content and merely self-connects via (finite/infinite) treelike chains, the coupling is undermined by overdamping of the in-chain stretching until a phonon exceptional point is reached at the resonance. Only the out-of-chain vibrations "survive" the resonance, the in-chain ones are "killed". This picture is not bond-related, and hence presumably generic to mixed crystals of the closing-type under pressure (dominant over the opening-type), indicating a key role of the mesostructure in the pressure dependence of phonons in mixed crystals.

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(Ga,In)P: A standard alloy in the classification of phonon mode behavior

Pagès¹,

Chafi²,

Fristot³

et al. 2006

Phys. Rev. B

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Contrary to a broadly accepted assumption we show that random (Ga,In)P is not an exception with respect to the crude classification of the phonon mode behavior of random mixed crystals in terms of 1-bond->1-mode systems or 2-bond->1-mode systems, as established from the simple criterion derived by Elliott et al. [Rev.Mod.Phys. 46, 465 (1974)]. Consistent understanding of the puzzling Raman/infrared behavior of (Ga,In)P, that has been a subject of controversy, is achieved via a basic version of our 1-bond->2-mode model. The Raman/infrared features from (Ga,In)P are accordingly re-assigned, with considerable change with respect to the previous approaches. Besides, we show that the idea of two bond lengths per species in alloys, supported by our 1-bond->2-phonon picture, opens an attractive area for the discussion of spontaneous ordering in GaInP_2, and in mixed crystals in general. The whole discussion is supported by detailed re-examination of the (Ga,In)P Raman/infrared data in the literature, full contour modeling of the transverse and longitudinal optical Raman lineshapes via our phenomenological 1-bond->2-mode model, and first-principles bond length calculations.Comment: 12 pages, 3 figures, submitted to Phys.Rev.

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Percolation model for long wave phonons in random zincblende alloys: from II‐VI's to III‐V's

Cited by 3 publications

References 11 publications

Exceptional phonon point versus free phonon coupling in Zn1−xBexTe under pressure: an experimental and ab initio Raman study

Exceptional phonon point versus free phonon coupling in Zn1−xBexTe under pressure: an experimental and ab initio Raman study

Exceptional Phonon Point Versus Free Phonon Coupling in Zn1-xBexTe Under Pressure: An Experimental and ab Initio Raman Study

(Ga,In)P: A standard alloy in the classification of phonon mode behavior

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