The influence of phonons and polarons on the infrared absorption of cadmium oxide

The lattice dynamics of rocksalt CdO is studied as a function of pressure using density-functional linear-response theory. The predicted static phase-transition pressure from rocksalt (B1) to CsCl (B2) structures is 76.12 GPa. Analysis of the phonon calculations suggests that the pressure-induced instabilities at p ¼ 78.26 GPa of the transverse acoustic (TA) modes in a large portion of the Brillouin zone are responsible for the phase transition from B1 ! B2 phases of CdO. Moreover, the calculated partial phonon density of states at the precursor phase transition of p ¼ 70 GPa reveals strong reduction of the longitudinal acoustic Cd-like modes and the existence of a large peak related to the longitudinal optic O-like mode.

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“…, in good agreement with the calculated [19] value of 267 cm À1 and with the experimental [20] one of 262 cm…”

supporting

confidence: 88%

“…, in good agreement with the calculated [19] value of 431 cm À1 , but lower than the experimental value of 523 cm À1 derived from the infrared measurements [20]. The PPDOS is characterized by four well-separated regions that are distinguished corresponding to transverse acoustic (TA), longitudinal acoustic (LA), TO, and longitudinal optic (LO) modes.…”

supporting

confidence: 60%

Pressure-induced instability in CdO

Aïdouni

Zaoui

Ferhat

2014

Phys. Status Solidi B

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“…This plasmon-phonon peak shifts to higher frequencies with increasing density, such that a double peak structure can appear in the 3D many-polaron optical absorption spectrum, consistent with the observed bimodal polaronic band in cadmium oxide. 38 As a first application of the method presented here, we chose to investigate the optical absorption of the interacting polaron gas in the RPA framework. For Nd 2 CuO 4Ϫ␦ (␦ Ͻ0.004), similarities were observed ͑see Fig.…”

Section: Discussionmentioning

confidence: 99%

Optical absorption of an interacting many-polaron gas

2001

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The optical absorption of a many ͑continuum͒ polaron gas is derived in the framework of a variational approach at zero temperature and weak electron-phonon coupling strength. We derive a compact formula for the optical conductivity of the many-polaron system, taking into account many-body effects in the electron or hole system. Within the method presented here, these effects are contained completely in the dynamical structure factor of the electron or hole system. This allows one to build on well-established studies of the interacting electron gas. Based on this approach a feature in the absorption spectrum of the many-polaron gas, related to the emission of a plasmon together with a phonon, is identified. As an application and illustration of the technique, we compare the theoretical many-polaron optical absorption spectrum as derived in the present work with the ''d-band'' absorption feature in Nd 2 CuO 4Ϫ␦ (␦Ͻ0.004). Similarities are shown between the theoretically and the experimentally derived first frequency moment of the optical absorption of a family of differently doped Nd 2Ϫx Ce x CuO 4 materials.

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“…Using a band edge effective mass of m * = 0.24m 0 and ε(∞) = 5.4 [13,32], a plasmon energy of E p = 245 meV for the annealed sample gives a carrier density of n = 5.9 × 10 19 cm −3 , whereas E p = 460 meV for the asgrown sample gives n = 2.5 × 10 20 cm −3 . The agreement with Hall measurement is excellent for the high carrier concentration sample, illustrating HAXPES bulk sensitivity, and suggests there is no significant contribution of extra carrier density from an electron accumulation layer.…”

Section: Core Levelsmentioning

confidence: 99%

Hard x-ray photoelectron spectroscopy as a probe of the intrinsic electronic properties of CdO

et al. 2014

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Hard x-ray photoelectron spectroscopy (HAXPES) is used to investigate the intrinsic electronic properties of single crystal epitaxial CdO(100) thin films grown by metal organic vapor phase epitaxy (MOVPE). The reduced surface sensitivity of the HAXPES technique relaxes stringent surface preparation requirements, thereby allowing the measurement of as-grown samples with intrinsically higher carrier concentration (n = 2.4 × 10 20 cm −3 ). High-resolution HAXPES spectra of the valence band and core levels measured at photon energy of 6054 eV are presented. The effects of conduction band filling and band gap renormalization are discussed to explain the observed binding energy shifts. The measured bandwidth of the partially occupied conduction band feature indicates that a plasmon contribution may be present at higher carrier concentrations. The Cd 3d 5/2 and O 1s core-level line shapes are found to exhibit an increased asymmetry with increased carrier concentration, interpreted as evidence for final state screening effects from the carriers in the conduction band. Alternatively the core-level line shape is interpreted as arising from strong conduction electron plasmon satellites. The nature of these two competing models to describe core-level line shapes in metallic oxides is explored.

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The influence of phonons and polarons on the infrared absorption of cadmium oxide

Cited by 45 publications

References 5 publications

Pressure-induced instability in CdO

Pressure-induced instability in CdO

Optical absorption of an interacting many-polaron gas

Hard x-ray photoelectron spectroscopy as a probe of the intrinsic electronic properties of CdO

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