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Reedyk, M.; Timusk, T.; Js, Xue; Je, Greedan

doi:10.1103/physrevb.45.7406

Cited by 22 publications

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“…is a rare earth. Measured in parallel geometry, this system shows clearly an evolution of electron-coupled phonon absorption with doping [9]. The doping-induced modes appear as antiresonances; their positions are indicated by the vertical dashed lines.…”

Section: Inset Called Parallel Geometry Henceforth] and The C-axis-pmentioning

confidence: 91%

“…Consequently the symmetry-allowed normal optical phonons are not well screened and appear as peaks in the optical conductivity (e.g., near 640, 355, 300, and 200 cm"'). The electroncoupled modes, on the other hand, absent in the undoped parent compound [9], appear as minima at 435, 525, and 585 cm"'.…”

Section: Inset Called Parallel Geometry Henceforth] and The C-axis-pmentioning

confidence: 94%

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Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

Reedyk

Timusk

1992

Phys. Rev. Lett.

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We show that the strong absorption structure observed in the a-^-plane optical conductivity of the high-Tc superconductors is correlated with c-axis longitudinal optical (LOc) phonons. This suggests a resolution to the long-standing controversy over the origin of these features. The interaction with LOc phonons is forbidden when the incident wave vector q is normal to the c axis which leads to the surprising result, confirmed with experiments, that the optical properties along a or b are different when measured on the fl-^-plane face and a face containing the c axis. PACS numbers: 74.30.Gn, 63.20.Kr, 74.70.Vy, 78.20.CiThe unconventional response of the high-Tc superconductors to electromagnetic radiation has been well established [1]. A prominent manifestation of the non-Drude behavior is the "knee" that develops in the a-6-plane reflectance of YBa2Cu307-5 near 400 cm "' at low temperatures leading to a '*notch"-like absorption feature in the optical conductivity [2,3]. This structure has been the focus of much discussion. It has been variously attributed to the superconducting energy gap [4] and to pho-It has become clear that YBaiCusOj-s is not the only cuprate superconductor to exhibit such structure. Bi2Sr2CaCu208 [6], Tl2Ba2Ca"-iCu"02"+4 [7,8], Pb2-Sr2(Y/Ca)Cu308 [9], and Nd2-xCe;cCu04-5 [10] all show strong low-frequency absorption features in the non-Drude component of the a-6-plane optical conductivity. In each case the structure appears as a minimum in (7\((o). There are, however, significant material to material diff'erences in the number, magnitude, width, and position of the minima. For example, whereas YBa2-CU3O7-5 is dominated by one broad feature near 420 cm~^ [ Fig. 2(b)], Tl2Ba2CaCu208 shows two deep minima at 350 and 600 cm~^ [ Fig. 3(b)], while Pb2Sr2(Y/Ca)Cu308 exhibits two closely spaced sharper minima at 525 and 585 cm "^ and a third broader feature centered near 435 cm ~' [Fig. 2(a)].The relative independence of the position of this structure to both temperature [3] and level of doping [2] suggests that it is unrelated to the superconducting energy gap and that phonons are involved. It has been shown that a sharp level, interacting with an electronic continuum, results in a notchlike minimum in the spectrum of the continuum (an antiresonance) if the external field does not interact with the sharp transition [11,12]. This phenomenon, discussed by Fano for atoms [11] and Rice for phonons and an electronic continuum [12], is common in quasi-one-dimensional organic conductors, where charge [13] or spin density [14] waves break symmetry and couple the low-lying charge-transfer continuum to totally symmetric phonon modes not normally ir active [12]. In high-T^c superconductors, the interaction of the phonons is with bound (midinfrared) and not Drude-like

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Section: Inset Called Parallel Geometry Henceforth] and The C-axis-pmentioning

confidence: 91%

Section: Inset Called Parallel Geometry Henceforth] and The C-axis-pmentioning

confidence: 94%

Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

Reedyk

Timusk

1992

Phys. Rev. Lett.

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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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“…These results strongly suggested that the origin of "notch"-like structures in σ ab is in the interaction of the a-b-plane electronic continuum with LO c phonons [2,3], rather than in superconducting gap(s) [4]. This was further corroborated by Reedyk et al [5] in a detailed analysis of their a-b-plane reflectivity measurements on the P b 2 Sr 2 LCu 3 O 8 -series (L = Y, Dy, Eu, Sm, N d, and P r), where an intrinsically low carrier concentration enables one to follow closely the progression of the phonon features as one goes from an insulating to a metallic regime. While the a-b-plane conductivity of the insulating compounds below 700 cm −1 is dominated by a series of infrared-active phonon peaks, the phonon peaks have by and large disappeared in the conductivity of metallic compounds due to screening and several antiresonant "notch"-like features appear at the positions of LO c phonons.…”

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confidence: 55%

Weak electron-phonon interaction and strong phonon features in a-b-plane optical conductivity of high-Tc superconductors

Kostur

Mitrović

1995

Journal of Physics and Chemistry of Solids

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Optical investigation of the metal-insulator transition in the Ca-freePb2Sr2

Cited by 22 publications

References 21 publications

Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

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

Weak electron-phonon interaction and strong phonon features in a-b-plane optical conductivity of high-Tc superconductors

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Optical investigation of the metal-insulator transition in the Ca-freePb2Sr2

Cited by 22 publications

References 21 publications

Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

Evidence fora-b-plane coupling to longitudinalc-axis phonons in high-Tcsuperconductors

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

Weak electron-phonon interaction and strong phonon features in a-b-plane optical conductivity of high-Tc superconductors

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Product

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About

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