Temperature dependence of the mid-infrared absorption in La1.84Sr0.16NiO4+δ

Crandles, D. A.; Timusk, T.; Garret, J.D.; Greedan, J. E.

doi:10.1016/0921-4534(93)90638-7

Cited by 20 publications

(16 citation statements)

References 19 publications

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“…In the absence of stripe order, a Hartree-Fock analysis of the doped nickelate would yield a metallic state, whereas numerous studies [16][17][18][19][20][21] have shown that even above the charge-ordering temperature the optical conductivity is dominated by midinfrared absorption bands, with no ϭ0 Drude component. Furthermore, neutron-diffraction studies of the ordered state have shown that in some cases the stripe spacing changes with temperature, 6,9 implying a variation in the charge density within a stripe.…”

Section: Introductionmentioning

confidence: 97%

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
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We report a detailed neutron-scattering study of the ordering of spins and holes in oxygen-doped La 2 NiO 4.133 . The single-crystal sample exhibits the same oxygen-interstitial order but better defined chargestripe order than that studied previously in crystals with ␦ϭ0.125. In particular, charge order is observed up to a temperature at least twice that of the magnetic transition, T m ϭ110.5 K. On cooling through T m , the wave vector ⑀, equal to half the charge-stripe density within an NiO 2 layer, jumps discontinuously from 1 3 to 0.2944. It continues to decrease with further cooling, showing several lock-in transitions on the way down to low temperature. To explain the observed lock-ins, a model is proposed in which each charge stripe is centered on either a row of Ni or a row of O ions. The model is shown to be consistent with the l dependence of the magnetic peak intensities and with the relative intensities of the higher-order magnetic satellites. Analysis of the latter also provides evidence that the magnetic domain walls ͑charge stripes͒ are relatively narrow. In combination with a recent study of magnetic-field-induced effects, we find that the charge stripes are all O centered at TϾT m , with a shift towards Ni centering at TϽT m . Inferences concerning the competing interactions responsible for the temperature dependence of ⑀ and the localization of charge within the stripes are discussed. ͓S0163-1829͑98͒00902-3͔

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Section: Introductionmentioning

confidence: 97%

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
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“…2 Katsufuji et al 3 showed for La 1.67 Sr 0.33 NiO 4 that spectacular changes occur on the scale of 1 eV as the temperature is changed from 10 K up to 480 K, the latter being twice the temperature at which the charge is know to order. 13 The mid-infrared (MIR) conductivity peak has been variously interpreted in terms of polarons, 3,4,5,6,7,8 d-d excitations, 8,9 a dopedsemiconductor, 10 and conventional charge-density-wave (CDW) ordering 3 ; however, none of these interpretations is particularly convincing.…”

Section: Introductionmentioning

confidence: 99%

“…1, 2,3,4,5,6,7,8,9,10,11,12 The substitution of Sr 2+ for La 3+ dopes holes into the NiO 2 plane. When the light polarization is parallel to the NiO 2 planes, the electronic conductivity exhibits a broad peak at ∼ 0.6 eV, 1 whose intensity grows with the hole concentration.…”

Section: Introductionmentioning

confidence: 99%

Mid-infrared conductivity from mid-gap states associated with charge stripes

Homes

Tranquada²,

Li³

et al. 2003

Phys. Rev. B

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The optical conductivity of La2−xSrxNiO4 has been interpreted in various ways, but so far the proposed interpretations have neglected the fact that the holes doped into the NiO2 planes order in diagonal stripes, as established by neutron and X-ray scattering. Here we present a study of optical conductivity in La2NiO 4+δ with δ = 2 15, a material in which the charge stripes order threedimensionally. We show that the conductivity can be decomposed into two components, a midinfrared peak that we attribute to transitions from the filled valence band into empty mid-gap states associated with the stripes, and a Drude peak that appears at higher temperatures as carriers are thermally excited into the mid-gap states. The shift of the mid-IR peak to lower energy with increasing temperature is explained in terms of the Franck-Condon effect. The relevance of these results to understanding the optical conductivity in the cuprates is discussed.

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“…4,24,28 In the case of the high-T c cuprate superconductors the MIR band softening was interpreted in terms of large polaron models including polaron-polaron interactions.…”

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confidence: 99%

Signatures of polaronic excitations in quasi-one-dimensionalLaTiO3.41

et al. 2003

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The optical properties of quasi-one-dimensional metallic LaTiO3.41 are studied for the polarization along the a and b axes. With decreasing temperature modes appear along both directions suggestive for a phase transition. The broadness of these modes along the conducting axis might be due to the coupling of the phonons to low-energy electronic excitations across an energy gap. We observe a pronounced midinfrared band with a temperature dependence consistent with (interacting) polaron models. The polaronic picture is corroborated by the presence of strong electron-phonon coupling and the temperature dependence of the dc conductivity.Titanium oxide compounds have been investigated extensively over the last decades, at the latest since the discovery of high-T c superconductivity in the cuprates, to study the role of electronic correlations and to explore the doping induced transition from a Mott insulator to a metal, like, e.g., in La 1−y Sr y TiO 3 .1,2 Of further interest are the titanates because of the proposed polaronic nature of their charge carriers. For example, the existence of small polarons in La 1−γ TiO 3±δ was shown by dc resistivity and thermoelectric power measurements.2,3 Signatures of polaronic carriers were also found in the optical response of TiO 2 , BaTiO 3 , and SrTiO 3 in the form of a midinfrared (MIR) band.4-8 Since a MIR band of (spin-) polaronic origin at ≈1000 cm −1 was also found in several cuprates 9-12 it seems to be a characteristic feature of this class of compounds for low doping as well. The proposal that (bi)polarons might play a major role for the high-T c superconductivity 13 stimulated a vast amount of experimental investigations on this issue.On the other hand, the nature of the polaronic carriers in the titanates is still under discussion. In this paper we present the optical properties of another titanium oxide compound, LaTiO 3.41 , to search for polaronic signatures and test their compatibility with the existing models. Indeed, we find a strong MIR band in the optical response showing a strong temperature dependence. A particular property of LaTiO 3.41 is its quasione-dimensional (quasi-1D) metallic character which was recently found by resistivity measurements.14 It is interesting to note that a MIR band was also observed for a variety of organic and anorganic quasi-1D metals, like

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Temperature dependence of the mid-infrared absorption in La1.84Sr0.16NiO4+δ

Cited by 20 publications

References 19 publications

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
View full text Add to dashboard Cite

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
View full text Add to dashboard Cite

Mid-infrared conductivity from mid-gap states associated with charge stripes

Signatures of polaronic excitations in quasi-one-dimensionalLaTiO3.41

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Temperature dependence of the mid-infrared absorption in La1.84Sr0.16NiO4+δ

Cited by 20 publications

References 19 publications

Neutron-diffraction study of stripe order inLa2NiO4+δwithWochner1, Tranquada2, Buttrey3 et al. 1998Phys. Rev. B121201211View full textAdd to dashboardCite

Neutron-diffraction study of stripe order inLa2NiO4+δwithWochner1, Tranquada2, Buttrey3 et al. 1998Phys. Rev. B121201211View full textAdd to dashboardCite

Mid-infrared conductivity from mid-gap states associated with charge stripes

Signatures of polaronic excitations in quasi-one-dimensionalLaTiO3.41

Contact Info

Product

Resources

About

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
View full text Add to dashboard Cite

Neutron-diffraction study of stripe order inLa2NiO4+δwith
Wochner
¹
,
Tranquada
²
,
Buttrey
³

et al. 1998
Phys. Rev. B
121
20
121
1
View full text Add to dashboard Cite