Investigation of k = 0 phonons in Bi, Cd, Mg, and Zn by Raman scattering

Grant, William B.; Schulz, Hartwig; Hüfner, S.; Pelzl, J.

doi:10.1002/pssb.2220600136

Cited by 33 publications

(19 citation statements)

References 44 publications

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“…5 (a), the amplitude of the coherent E 2g phonon significantly decreases upon increasing the lattice temperature. The decrease in the amplitude of the coherent optical phonon at higher temperatures is contrary to the temperature dependence of the Raman intensity, [21,32] confirming that the amplitude of the nonequilibrium coherent phonon is not determined by Bose-Einstein statistics n k = 1/[exp( Ω 0 /k B T ) − 1], which shows an increase in the phonon occupation number at higher temperatures. The very close behavior of the temperature dependence of the phonon and electronic [see below in Fig.…”

Section: Temperature Dependence Of Damping and Frequency Of The E2g Modementioning

confidence: 91%

“…Appropriate candidates of the metallic samples that meet the above requirements, are Zn, Cd, and Mg, in which k = 0 optical phonon modes were, in fact, observed in Raman scattering. [21] In this paper, we report on the observation of both bulk coherent optical phonon and nonequilibrium electrons in Zn and Cd using a femtosecond pump-probe reflectivity technique with high sensitivity of ∆R/R = 10 −7 . The coherent E 2g phonon, whose oscillatory frequency is in the terahertz region, is generated by optical excitation of nonequilibrium electrons (interband transition).…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast dynamics of coherent optical phonons and nonequilibrium electrons in transition metals

et al. 2005

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The femtosecond optical pump-probe technique was used to study dynamics of photoexcited electrons and coherent optical phonons in transition metals Zn and Cd as a function of temperature and excitation level. The optical response in time domain is well fitted by linear combination of a damped harmonic oscillation because of excitation of coherent E2g phonon and a subpicosecond transient response due to electron-phonon thermalization. The electron-phonon thermalization time monotonically increases with temperature, consistent with the thermomodulation scenario, where at high temperatures the system can be well explained by the two-temperature model, while below ≈ 50 K the nonthermal electron model needs to be applied. As the lattice temperature increases, the damping of the coherent E2g phonon increases, while the amplitudes of both fast electronic response and the coherent E2g phonon decrease. The temperature dependence of the damping of the E2g phonon indicates that population decay of the coherent optical phonon due to anharmonic phononphonon coupling dominates the decay process. We present a model that accounts for the observed temperature dependence of the amplitude assuming the photoinduced absorption mechanism, where the signal amplitude is proportional to the photoinduced change in the quasiparticle density. The result that the amplitude of the E2g phonon follows the temperature dependence of the amplitude of the fast electronic transient indicates that under the resonant condition both electronic and phononic responses are proportional to the change in the dielectric function.

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Section: Temperature Dependence Of Damping and Frequency Of The E2g Modementioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of coherent optical phonons and nonequilibrium electrons in transition metals

et al. 2005

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“…10 However, experimental investigation of the Fano interference in metals has been inaccessible by conventional time-integrated methods like Raman scattering. 11,12 This can be attributed to either the very fast dephasing of the electronic continuum or to screening of electron-phonon coupling.…”

mentioning

confidence: 99%

“…The extracted frequency of the coherent optical phonon is found to be 2.30 THz at 0.68 mJ/ cm 2 , in excellent agreement with that of the E 2g mode observed by Raman scattering. 11 At high fluences, however, the coherent response cannot be fitted by a simple damped oscillator over the entire time range. In fact, there is a significant phase shift of the coherent phonon at the early time delays, which cannot be modeled by a simple damped oscillator.…”

mentioning

confidence: 99%

Photoinduced Fano resonance of coherent phonons in zinc

2006

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Utilizing femtosecond optical pump-probe technique, we have studied transient Fano resonance in zinc. At high excitation levels the Fourier spectrum of the coherent E 2g phonon exhibits strongly asymmetric line shape, which is well modeled by the Fano function. The Fano parameter ͑1/Q͒ was found to be strongly excitation fluence dependent while depending weakly on the initial lattice temperature. We attribute the origin of the Fano resonance to the coupling of a coherent phonon to the electronic continuum, with their transition probabilities strongly renormalized in the vicinity of the photoinduced structural transition.

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“…Пошуки таких ефектів проводилися для Zn [121,122], Cd [121], Be [123]. Експерименти в цих металах виявили збільшення енергій і звуження ширин фононних ліній при охоло-дженні і дозволили оцінити внески ангармонізму і електрон-фононної взаємодії в частотні зсуви і загасання фононів при низьких температурах.…”

Section: температурна та концентраційна залежності спектру частот колunclassified

Influence of an Anharmonicity and Electron–Phonon Interaction on a Frequency Spectrum of Crystals with the Hexagonal Close-Packed Lattice

2011

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В огляді розглянуто основні методи опису енергетичного спектру електро-нів та спектру частот коливань атомів кристалічної ґратниці. Зроблено огляд основних метод дослідження впливу ефектів ангармонізму на фізич-ні властивості матеріялів та спектер частот коливань кристалічної ґратни-ці. Описано самоузгоджене гармонічне наближення, що базується на мето-ді двочасових Ґрінових функцій. В рамках цього наближення записано рі-внання руху для Ґрінових функцій «зміщення-зміщення», яке схоже на рівнання руху в гармонічному наближенні, але силові постійні будуть пе-ренормованими і визначаться термодинамічним усередненням других по-хідних потенціялу, а не їх рівноважним значенням. Досліджено вплив ефектів ангармонізму та електронної підсистеми на спектер частот криста-лічної ґратниці гексагонального щільнопакованого кристалу Ti 0,93 Al 0,07 .In a given review, the basic methods for description of the energy spectrum of electrons and the frequency spectrum of atomic vibrations of the crystal lattice are considered. The basic methods for investigation of influence of the anharmonicity effects on the physical properties of materials and a frequency spectrum of vibrations of the crystal lattice are reviewed. The self-consistent harmonic approximation, which is based on the method of double-time Green's functions, are described. Within the scope of this approximation, the equation of motion for the 'displacements-displacements' Green's functions, which is similar to the equation of motion in the harmonic approximation, is derived, but the force constants are renormalized and are determined by the thermodynamical averaging of second derivatives of potential rather than their equilibrium values. Appearances of the anharmonicity effects in the vibrational spectrum of the Ti 0.93 Al 0.07 hexagonal close-packed crystal lattice Успехи физ. мет. / Usp. Fiz. Met. 2011, т. 12, сс. 389-450 Îòòèñêè äîñòóïíû íåïîñðåäñòâåííî îò èçäàòåëÿ Ôîòîêîïèðîâàíèå ðàçðåøåíî òîëüêî â ñîîòâåòñòâèè ñ ëèöåíçèåé 2011 ÈÌÔ (Èíñòèòóò ìåòàëëîôèçèêè èì. Ã. Â. Êóðäþìîâà ÍÀÍ Óêðàèíû) Íàïå÷àòàíî â Óêðàèíå.

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Investigation of k = 0 phonons in Bi, Cd, Mg, and Zn by Raman scattering

Cited by 33 publications

References 44 publications

Ultrafast dynamics of coherent optical phonons and nonequilibrium electrons in transition metals

Ultrafast dynamics of coherent optical phonons and nonequilibrium electrons in transition metals

Photoinduced Fano resonance of coherent phonons in zinc

Influence of an Anharmonicity and Electron–Phonon Interaction on a Frequency Spectrum of Crystals with the Hexagonal Close-Packed Lattice

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