Pressure shift of the zone-center TO mode of Zn

Olijnyk, H.; Jephcoat, A. P.; Novikov, D. L.; Christensen, N. E.

doi:10.1103/physrevb.62.5508

Cited by 47 publications

(49 citation statements)

References 34 publications

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“…Since the E 2g mode in Zn may be sensitive to highly anisotropic compressional behavior of c/a axial ratio in Zn crystal (hcp structure), as observed by Raman scattering under pressure, controlling the amplitude and the frequency of the coherent E 2g phonon will be useful for the study of the gradual anisotropic → isotropic transition occuring in Zn. [45] we obtain net pulse duration ∆τ from the pulse duration of AC ∆τAC, where ∆τ = ∆τAC × 0.648 (See Ref. [2]).…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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

et al. 2005

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“…They have been discovered as residuals in the chemical processing [197,198] with the disruption of a "neck" in the σ Fermi surface with the critical point at E F =E Γ therefore this transition will be studied here as a function of the Lifshitz parameter z=E Γ -E F . The influence of the proximity to a type (II) electronic topological transition on the anomalous electronic and lattice properties of MgB 2 is shown by the anomalous pressure dependence of the E 2g phonon mode and T c (202,203). The response of the superconducting properties of diborides to Fermi level tuning has been studied by electron doping using atomic substitutions, in fact it is possible to reduce the number of holes in the σ band from about 0.15 holes per unit cell in MgB 2 up to reach zero σ holes at the top of the σ band where E F =E A .…”

Section: Feshbach Shape Resonances In Diboridesmentioning

confidence: 99%

Feshbach Shape Resonance in Multiband Superconductivity in Heterostructures

Bianconi¹

2005

J Supercond

117

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We report experimental data showing the Feshbach shape resonance in the electron Van Hove-Lifshits feature for the change of Fermi surface dimensionality in the electronic energy spectrum in one of the subbands. In this heterostructure at atomic limit the multiband superconductivity is in the clean limit because the disparity and negligible overlap between electron wavefunctions in different subbands suppresses the single electron interband impurity scattering rate. The emerging scenario from these 2 experimental data suggests that the Feshbach shape resonance could be the mechanism for high T c in particular nanostructured architectures.

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“…4). The systematic offset of the calculated frequencies by Ϸ20 cm Ϫ1 (Ͻ10%) is typical for a comparison of computed and measured phonon frequencies (28). The magnitude of splitting predicted here is related to afmII, but other magnetic structures will also result in splitting of the TO mode.…”

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confidence: 99%

Magnetism in dense hexagonal iron

Steinle‐Neumann

Stixrude

Cohen

2003

Proc. Natl. Acad. Sci. U.S.A.

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The magnetic state of hexagonal close-packed iron has been the subject of debate for more than three decades. Although Mö ssbauer measurements find no evidence of the hyperfine splitting that can signal the presence of magnetic moments, density functional theory predicts an antiferromagnetic (afm) ground state. This discrepancy between theory and experiment is now particularly important because of recent experimental findings of anomalous splitting in the Raman spectra and the presence of superconductivity in hexagonal close-packed iron, which may be caused by magnetic correlations. Here, we report results from first principles calculations on the previously predicted theoretical collinear afm ground state that strongly support the presence of afm correlations in hexagonal close-packed iron. We show that anomalous splitting of the Raman mode can be explained by spinphonon interactions. Moreover, we find that the calculated hyperfine field is very weak and would lead to hyperfine splitting below the resolution of Mö ssbauer experiments. P hysical properties of iron are of great importance to many fields in the sciences, as iron is one of the most abundant and stable elements in the universe and the very basis for the steel industry. Hexagonal close-packed (hcp) iron, the form stable at high pressure, plays a central role in geophysics, as the Earth's inner core is thought to be primarily composed of this phase (1, 2), and in our understanding of impact and explosive phenomena in iron and steel (3). The magnetic state of iron has a major influence on the physics of iron and iron alloys, including the relative stability of the iron polymorphs (4, 5). The magnetic structure of the hcp phase has been the subject of a scientific debate for three decades (6), leading to contradictory results from experiments and theory. Although experiments are interpreted to show the absence of magnetism in hcp iron (6-10), computations based on density functional theory find an antiferromagnetic (afm) ground state stable to Ϸ50 GPa (11), similar to magnetism in the double hcp phase (5). The possible presence of magnetism in hcp iron as further substantiated in this article has important implications. In geophysics many experiments are carried out on potentially magnetic hcp iron and are then extrapolated to pressures of Earth's core, into the nonmagnetic region of the hcp stability field at high pressure, and may consequently not be valid. The possible presence of magnetism in hcp iron also plays an important role in the discussion of the recently observed superconductivity of hcp iron (12, 13): Magnetic correlations in hcp iron appear to be necessary to explain the observed pressure dependence of its superconductivity (14-16).The two lower-pressure polymorphs of iron are both magnetic. The phase stable around ambient conditions, body-centered cubic (bcc), owes its stability entirely to the presence of ferromagnetism (4). Heating above the Curie temperature causes the spins to disorder and the net magnetization to vanish, but the ind...

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Pressure shift of the zone-center TO mode of Zn

Cited by 47 publications

References 34 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

Feshbach Shape Resonance in Multiband Superconductivity in Heterostructures

Magnetism in dense hexagonal iron

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