Reedyk, Timusk, and Basov reply

Reedyk, M.; Timusk, T.; Basov, D. N.

doi:10.1103/physrevlett.71.2677

Cited by 16 publications

(21 citation statements)

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“…The broad, weak mode at ≈ 408 cm −1 has been observed in ceramic spectra of samples that appear to have been oxygen reduced [12], but this mode does not correspond to any of the calculated B 1u normal modes [39,40]. A similar mode is seen in YBa 2 Cu 4 O 8 [54] as well as in Pb 2 Sr 2 RCu 3 O 8 [55]. The common element in the three compounds is the third copper layer with two-fold coordinated oxygen bonds.…”

Section: The 400 CM −1 Modementioning

confidence: 84%

“…It would then not be unreasonable to anticipate that when the symmetry-breaking transition sets in at 150 K in the oxygen-reduced materials, that some of this phonon-driven charge is transferred from the O(4) and plane modes, to the newly activated breathing mode. The difficulty with this argument is that it is does not apply to the other two compounds where this mode is observed [54,55].…”

Section: The 400 CM −1 Modementioning

confidence: 99%

“…Broad minima in the ab-plane optical conductivity are seen at frequencies that are in the phonon region. These have been shown to be associated with c-axis longitudinal optic (LO) phonons [20,21] that couple to the ab-plane conductivity by a symmetry-breaking mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Homes¹,

Timusk²,

Bonn³

et al. 1995

Can. J. Phys.

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The c-axis polarized phonon spectra of single crystals of YBa2Cu3O6+x, were measured for the doping range x = 0.5 → 0.95, between 10 K and 300 K. The low background electronic conductivity, determined by Kramers-Kronig analysis of the reflectance, leads to a rich phonon structure. With decreased doping the five normally-active B1u modes broaden and the high-frequency apical oxygen mode splits into two components. We associate the higher of these with the two-fold coordinated copper "sticks". The 155 cm −1 low-frequency mode, which involves the apical and the chainoxygens, splits into at least three components with decreasing doping. Some phonon anomalies which occur near Tc in the highly-doped material occur well above Tc in the oxygen-reduced systems. An unusual broad phonon band develops in the normal state at ≈ 400 cm −1 , which becomes more intense at low doping and low temperatures, borrowing oscillator strength from apical and plane oxygen modes resulting in a major transformation of the phonon spectrum below ≈ 150 K.Résumé : Les spectres de phonons polarisés suivant l'axe c, dans des monocristaux de YBa2Cu3O6+x ontété measurés, pour l'intervalle de dopage x = 0, 5à 0, 95, entre 10 et 300 K. La faible condutivitéélectronique de fond, déterminée par analyse Kramers-Kronig de la réflectance, donne lieuà une riche structure de phonons. Lorsqu'on diminue le dopage, les cinque modes B1u normalement actifs s'élargissent, et le mode apicalà haute fréquence de l'oxygène se divise en deux composantes. Nous associons la plus haute de ces composantes aux « bâtons » de cuivreà coordinence deux. Le mode de basse fréquence,à 155 cm −1 , qui implique les oxygènes apical et en chaîne, se sépare en au moins trois composantes lorsque le dopage diminue. Certaines anomalies de phonons, présentes au voisinage de Tc dans les cristaux faiblement dopés, apparaissentà des températures bien plus grandes que Tc dans les systèmes avec moins de l'óxygène. A environ 400 cm −1 , il se développe dans l'état normal une bande large insolite qui devient plus intenseà faible dopage et a basse température, avec une force d'ocsillateur empruntée aux modes apical et plan de l'oxygène, ce quie entraîne une transformation majeure des spectres de phonons au-dessous d'environ 150 K.[Traduit par la rédaction]

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Section: The 400 CM −1 Modementioning

confidence: 84%

Section: The 400 CM −1 Modementioning

confidence: 99%

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Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Homes¹,

Timusk²,

Bonn³

et al. 1995

Can. J. Phys.

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“…Moreover, in the 400-600 cm −1 region of the reflectivity spectra of Pb 2 Sr 2 LCu 3 O 8 (L = Y, Dy, Eu, Nd, and Pr), phonon lineshapes have been reported to become asymmetric for increasing doping. 8 These results have been explained in terms of an interaction of Ramanactive modes along the c−axis, made infrared-active by some symmetry-breaking potential, and an electronic continuum which develops with doping in the mid infrared. As far as we know, no evidence of Fano lineshapes has been reported for the four infrared active E u phonons of the a − b plane.…”

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confidence: 99%

Fano effect in thea−bplane ofNd1.96Ce0.04
Lupi
¹
,
Capizzi
²
,
Calvani
³

et al. 1998
Phys. Rev. B
45
1
29
0
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Reflectance measurements in properly selected samples of Nd 1.96 Ce 0.04 CuO 4+y with different carrier concentrations provide a firm evidence of Fano antiresonances for the four transverse optical E u phonons in the a − b plane. A fit of the whole optical conductivity has been performed, without any previous subtraction of the electronic background. Those fits, as well as the dependence on temperature of the renormalized phonon frequencies, show that the electronic continuum is provided by the same polaron band which characterizes the optical conductivity of all the insulating parent compounds of high T c superconductors. The relevance of these results for the metallic and superconducting phase of cuprates is discussed. 74.30.Gn, 72.10Di, 74.70Vy, 78.20C

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“…Measurements on dc resistivity for underdoped samples also reveal that the inplane resistivity ρ ab (T ) deviates from a linear in temperature behavior at some temperature consistent with the crossover temperatures T * in NMR experiments [11]. On the other hand, the c-axis optical conductivity σ c (ω) [12][13][14][15] exhibits a striking gap-like depression at low frequency and the c-axis resistivity ρ c (T ) displays a upturn semiconducting feature [11] in the normal-state underdoped samples, characteristic of the formation of some kinds of gap.…”

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confidence: 73%

Normal-state magnetic susceptibility in a bilayer cuprate

Statt

Hsueh

et al. 1997

Phys. Rev. B

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The magnetic susceptibility of high-Tc superconductors is investigated in the normal state using a coupled bilayer model. While this model describes in a natural way the normal-state pseudogaps seen in c-axis optical conductivity on underdoped samples, it predicts a weakly increasing susceptibility with decreasing temperature and cannot explain the magnetic pseudogaps exhibited in NMR measurements. Our result, together with some experimental evidence suggest that the mechanism governing the c-axis optical pseudogap is different from that for the a-b plane magnetic pseudogap.PACS numbers: 74.80. Dm, 74.25.Jb, Normal-state pseudogaps of underdoped samples have been one of the important subjects in the study of high-T c cuprates in the past few years [1]. Experimentally strong decrease of NMR Knight shift and spin-lattice relaxation rate with decreasing temperature has been observed in various normal-state underdoped samples below some cross over temperature T * [2-6]. These decreases have often been considered in terms of the opening of a "spin gap" due to the antiferromagnetic (AF) spin fluctuations [7][8][9] or, alternatively, the notion of "preformed Cooper pairs" in the case of significant order parameter phase fluctuations [10]. Measurements on dc resistivity for underdoped samples also reveal that the inplane resistivity ρ ab (T ) deviates from a linear in temperature behavior at some temperature consistent with the crossover temperatures T * in NMR experiments [11]. On the other hand, the c-axis optical conductivity σ c (ω) [12][13][14][15] exhibits a striking gap-like depression at low frequency and the c-axis resistivity ρ c (T ) displays a upturn semiconducting feature [11] in the normal-state underdoped samples, characteristic of the formation of some kinds of gap.A central question in the study of pseudogaps is -are the pseudogaps seen in the c-axis optical conductivity related at all to the magnetic pseudogaps seen in NMR experiments? Or, could there be two different mechanisms? While there is currently no consensus on this point, we begin by comparing first some of the properties of these two pseudogaps seen in experiments. Consider the magnitude and anisotropy of these two pseudogaps: (i) Magnitude -Although one does not measure the magnetic pseudogap directly, an analysis done by Williams et al.[16] of Knight-shift data based on quasiparticle excitation spectrum given by1/2 where ∆ k is the normal-state pseudogap shows that the magnitude of magnetic pseudogap is strongly dependent on doping or carrier density (larger gap with lower doping) and scales with the crossover temperature T * . In contrast, the c-axis optical conductivity measured by Homes et al.[13] on YB 2 C 3 O 6+x (YBCO) at different doping x indicates that the frequency ranges where conductivity is suppressed (direct measurement for the size of the gap) are almost independent of doping. Moreover, a compari- [17] result), while the flat spectral weight seen within the pseudogap region in c-axis optical data implies that the optical ps...

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Reedyk, Timusk, and Basov reply

Cited by 16 publications

References 3 publications

Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Fano effect in thea−bplane ofNd1.96Ce0.04
Lupi
¹
,
Capizzi
²
,
Calvani
³

et al. 1998
Phys. Rev. B
45
1
29
0
View full text Add to dashboard Cite

Normal-state magnetic susceptibility in a bilayer cuprate

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Reedyk, Timusk, and Basov reply

Cited by 16 publications

References 3 publications

Optical phonons polarized along the c axis of YBa2Cu3O6+x, for x = 0.5 → 0.95

Optical phonons polarized along the c axis of YBa2Cu3O6+x, for x = 0.5 → 0.95

Fano effect in thea−bplane ofNd1.96Ce0.04Lupi1, Capizzi2, Calvani3 et al. 1998Phys. Rev. B451290View full textAdd to dashboardCite

Normal-state magnetic susceptibility in a bilayer cuprate

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Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Optical phonons polarized along the c axis of YBa₂Cu₃O_6+x, for x = 0.5 → 0.95

Fano effect in thea−bplane ofNd1.96Ce0.04
Lupi
¹
,
Capizzi
²
,
Calvani
³

et al. 1998
Phys. Rev. B
45
1
29
0
View full text Add to dashboard Cite