Infrared optical conductivity of the Nd-Ce-Cu-O system

Lupi, S.; Calvani, P.; Capizzi, M.; Maselli, P.; Sadowski, W.; Wałker, E.

doi:10.1103/physrevb.45.12470

Cited by 52 publications

(61 citation statements)

References 34 publications

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“…Increasing the charge density, we find that the optical absorption, in agreement with experimental data in the metallic phase of the cuprates [18][19][20] , is more and more controlled by the Drude-like term and, only for very high electron densities, no signature of the b) contribution is left .…”

Section: The Resultssupporting

confidence: 88%

Optical properties of an interacting large polaron gas

1999

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The normal state conductivity, σ(ω), of a system of interacting large polarons is calculated within the Random Phase approximation and some numerical results are presented. The behaviour of the optical absorption as a function of the charge carrier density and of the temperature is analyzed for different values of the electron-phonon coupling constant. It is shown that σ(ω) exhibits features similar to those observed in the infrared spectra of the cuprates.71.38: polarons and electron-phonon interaction 1

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Section: The Resultssupporting

confidence: 88%

Optical properties of an interacting large polaron gas

1999

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“…4 has been observed in previous work. 23,28,30 The location of this feature is similar to the onset of absorption in La 2 CuO 4 and related materials 37 at ≈ 11 000 cm −1 (≈ 1.4 eV). The peak is characteristic of a semiconducting band edge or a polaronic excitation.…”

Section: A Electronic Propertiessupporting

confidence: 55%

“…19 In fact, due to the sigTypeset by REVT E X nificant exchange interactions between the Pr ions which are mediated through the copper-oxygen layers, there is a Pr contribution to the susceptibility 12 below ≈ 200 K. The optical properties of Nd 2 CuO 4 have been investigated in ceramics and single crystals. 20,21,22,23,24,25,26,27 Single crystals of Pr 2 CuO 4 have been studied at either room temperature 28,29,30,31 or at low temperature 11,32 (≈ 10 K), but there has been no detailed investigation of the temperature dependence of the optical properties of this material. Furthermore, there is some disagreement in the literature with respect to the vibrational parameters of the E u modes.…”

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confidence: 99%

Infrared optical properties ofPr2CuO4

Homes

Fournier

et al. 2002

Phys. Rev. B

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The ab-plane reflectance of a Pr2CuO4 single crystal has been measured over a wide frequency range at a variety of temperatures, and the optical properties determined from a Kramers-Kronig analysis. Above ≈ 250 K, the low frequency conductivity increases quickly with temperature; ρ dc ≈ 1/σ1(ω → 0) follows the form ρ dc ∝ exp(Ea/kBT ), where Ea ≈ 0.17 eV is much less than the inferred optical gap of ≈ 1.2 eV. Transport measurements show that at low temperature the resistivity deviates from activated behavior and follows the form ρ dc ∝ exp[(T0/T ) 1/4 ], indicating that the dc transport in this material is due to variable-range hopping between localized states in the gap. The four infrared-active Eu modes dominate the infrared optical properties. Below ≈ 200 K, a striking new feature appears near the low-frequency Eu mode, and there is additional new fine structure at high frequency. A normal coordinate analysis has been performed and the detailed nature of the zone-center vibrations determined. Only the low-frequency Eu mode has a significant Pr-Cu interaction. Several possible mechanisms related to the antiferromagnetism in this material are proposed to explain the sudden appearance of this and other new spectral features at low temperature.

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“…34 Three distinct absorption bands can be distinguished: the ''d band'' ͑around 1000 cm Ϫ1 ), the midinfrared band ͑MIR, around 5000 cm Ϫ1 ), and the charge-transfer band ͑CT, around 10 4 cm Ϫ1 ). 8 Of all these features, the d band and, at a higher temperatures, the Drude-like component have ͑hypo-thetically͒ been associated with large polaron optical absorption. 5,7,14 For the lowest levels of Ce doping, the d band can be most clearly distinguished from the other features.…”

Section: Comparison To the Infrared Spectrum Of Nd 2àx Ce X Cuomentioning

confidence: 98%

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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Infrared optical conductivity of the Nd-Ce-Cu-O system

Cited by 52 publications

References 34 publications

Optical properties of an interacting large polaron gas

Optical properties of an interacting large polaron gas

Infrared optical properties ofPr2CuO4

Optical absorption of an interacting many-polaron gas

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