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Uchida, S.; Ido, T.; Takagi, H.; Arima, T.; Tokura, Y.; Tajima, S.

doi:10.1103/physrevb.43.7942

Cited by 1,000 publications

(781 citation statements)

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“…Despite the general consensus that the superconducting cuprate is metallic in the CuO 2 plane (ab-plane) but insulating in the direction perpendicular to the ab-plane (c-axis), which leads to a cylindrical Femi surface, recent quantum oscillations measurements of Y 1 Ba 2 Cu 3 O 6.5 [2] and Y 1 Ba 2 Cu 4 O 8 [3], which directly probe the free electrons (or holes) in the CuO 2 plane, found on the one hand that the area of the twodimensional (2D) Fermi surface is only 2 and 2.4 % of the total area of the Brillouin zone respectively, corresponding roughly to ~ 3 % of total doping-induced electrons when compared with the large Fermi surface observed in the over-doped regime [2]. On the other hand, the reported optical plasma frequency falls in the range of ~ 1.0 eV for all cuprates and is peculiarly insensitive to the doping levels ranging from underdoped to overdoped regimes [4].…”

mentioning

confidence: 90%

“…The real part of the conductivity (σ 1 ) and the real part of the dielectric function (ε 1 ) were calculated using a Kramers-Kronig transformation of the reflectivity data. For the high frequency extrapolation we have used the optical data reported [4] whereas the Hagen-Ruben's rule was used for the low frequency extrapolation. It turns out that the spectral features presented in this paper are insensitive to the extrapolations outside the spectral range of interest.…”

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confidence: 99%

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In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

Kim¹,

Hor²,

Dong³

et al. 2013

Solid State Communications

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We addressed the inconsistency between the electron mass anisotropy ratios determined by the far-infrared experiments and DC conductivity measurements. By eliminating possible sources of error and increasing the sensitivity and resolution in the far-infrared reflectivity measurement on the single crystalline and on the polycrystalline La 1.84 Sr 0.16 CuO 4 , we have unambiguously identified that the source of the mass anisotropy problem is in the estimation of the free electron density involved in the charge transport and superconductivity. In this study we found that only 2.8 % of the total doping-induced charge density is itinerant at optimal doping.Our result not only resolves the mass anisotropy puzzle but also points to a novel electronic structure formed by the rest of the electrons that sets the stage for the high temperature superconductivity.

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confidence: 90%

mentioning

confidence: 99%

In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

Kim¹,

Hor²,

Dong³

et al. 2013

Solid State Communications

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“…Conductivity is related to metal-metal (MM) CT between adjacent, equivalent sites in different oxidation states, in the present case the three oxidation states of copper Cu(I), Cu(II), and Cu(III) [6]. The neglect of negative terms in the expression for Hubbard-U [7] made it impossible for a long time to explain U < 0 [8] and why spectral density at 2 eV is moved to lower energies (<0.8 eV) after doping [9]. Finally, the electronic configuration interaction (CI) between the charged and spin-coupled states, which is a necessary condition for a superconducting (SC) phase [10], has not been widely recognized.…”

Section: Introductionmentioning

confidence: 99%

“…Equation 4 is the MMCT transfer transition at hν = 2.0 eV [19]. In the optimally doped system, there is a minimum in the far infrared optical conductivity at about 300 cm −1 in [20][21][22][23] and La 2−x Sr x CuO 4 [9], probably due to the SC gap. For 800>ν>300 cm −1 , the absorption is due to (4) since it cannot be due to (2), which is independent of doping and at 0.135 eV (∼ 1100 cm −1 ) [14].…”

Section: Introductionmentioning

confidence: 99%

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Larsson

2016

J Supercond Nov Magn

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Simulation of the resistivity in the normal state of doped La 2−x Sr x CuO 4 has been performed using a hopping model based on Marcus theory. The results are in substantial agreement with experimental results. At oxidative doping, Cu(III) sites are formed and electron mobility possible due to hopping: Cu(III)Cu(II) → Cu(II)Cu(III) (one-electron exchange). In the underdoped, non-metallic region, the resistivity (ρ) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. ρ then increases more than linearly with T (∼ T 3/2 ) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + hν → Cu(I) + Cu(III) is responsible for the strong absorption in the visible spectrum of La 2 CuO 4 . The down-shift of spectral density with doping (x) in La 2−x Sr x CuO 4 depends on the appearance of Cu(III) sites which makes optical as well as thermal one-electron exchange transitions possible with lower energy. Disproportionation occurs spontaneously for x > 0.06, opening up for electron pair formation. Configuration interaction between two-electron states of low chemical potential, but strong vibrational coupling, gives rise to the superconductor and pseudogaps. Data from photo-induced conductivity and absorption spectra are used in the simulation, which gives results in good agreement with experiments. Possible explanations for Raman and MIR absorption suggest themselves.

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“…We will discuss them shortly here. There exists much evidence coming from the research on optical conductivity [42,43] that in the low doping range the carrier density is proportional to the doped-hole concentration. The measurements of the penetration depth performed by means of the µSR technique demonstrated the proportionality between the hole density and the superfluid density [44].…”

Section: Origin Of the Small Nodal Pseudogapmentioning

confidence: 99%

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

et al. 2010

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We argue that three gaps observed in underdoped cuprates can be attributed to the formation of antiferromagnetic spin polarons and bipolarons. Within the spin polaron scenario the antinodal pseudogap at he high energy scale originates from the change of the Fermi surface topology, induced by antiferromagnetic correlations. That change gives rise to the diminishing of the spectral weight at the antinodal region near the Brillouin zone boundary. We demonstrate that effect by analyzing effective models of doped antiferromagnets. The second type of pseudogap appearing at the intermediate energy scale originates from the phenomena which are precursory to superconductivity and predominantly concern the portion of the Fermi surface near the nodal region. In order to analyze the latter phenomenon we use the negative U Hubbard model, in which many details typical to spin polaron physics are neglected, but which contains the essential ingredient of it, that is the strong short range attraction. The lowest energy scale is related to the true superconducting gap which develops with doping, although both types of pseudogap diminish with doping. This behavior can be explained by the fact that the spin polaron band is empty in the undoped system and therefore the formation of the superconducting state in the system is forbidden. Due to a pedagogical character of this report, we present in the introduction a short overview of mostly recent experimental results which are related to the gap-pseudogap physics.

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Optical spectra ofLa2−xSr
S. Uchida
¹
,
T. Ido
²
,
H. Takagi
³

et al.

Cited by 1,000 publications

References 36 publications

In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

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Optical spectra ofLa2−xSrS. Uchida1, T. Ido2, H. Takagi3 et al.

Cited by 1,000 publications

References 36 publications

In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

In-plane and out-of-plane plasma resonances in optimally doped La1.84Sr0.16CuO4

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

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Product

Resources

About

Optical spectra ofLa2−xSr
S. Uchida
¹
,
T. Ido
²
,
H. Takagi
³

et al.