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Schlesinger, Z.; Collins, R. T.; Holtzberg, F.; Feild, C.; Blanton, S. H.; Welp, U.; Crabtree, G. W.; Fang, Y.; Jz, Liu

doi:10.1103/physrevlett.65.801

Cited by 444 publications

(118 citation statements)

References 18 publications

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“…Reflectivity measurements on strongly oxygen disordered samples give γ as low as 1.05 [22]. We conclude that the Cu-O chains in our crystal are slightly disrupted by a small concentration of oxygen vacancies or impurities.…”

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confidence: 71%

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
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A small angle neutron scattering study of the flux-line lattice in a large single crystal of untwinned YBa2Cu3O 7−δ is presented. In fields parallel to the c-axis, diffraction spots are observed corresponding to four orientations of a hexagonal lattice, distorted by the a-b anisotropy. A value for the anisotropy, the penetration depth ratio, of λa/λ b =1.18(2) was obtained. The high quality of the data is such that second order diffraction is observed, indicating a well ordered FLL. With the field at 33 • to c a field dependent re-orientation of the lattice is observed around 3T.PACS numbers: 74.60. Ge, 74.72.Bk, 61.12.Ex The remarkable properties of the mixed state in the cuprate high-T c superconductors are of great current interest. In particular, the expectation that high-T c superconductors have an unconventional pairing symmetry has led inevitably to the question: how does the structure of the flux-line lattice (FLL) differ between conventional and unconventional superconductors? The question has been taken up by several recent theoretical contributions [1][2][3][4] which predict a variety of interesting FLL effects all deviating from the benchmark triangular Abrikosov lattice. However, such discussions may presuppose that the crystallographic properties of the FLL are already well understood in the simplest low-field regime where unconventional effects are least prevalent. This has been far from the experimental truth. Observations require a probe sensitive to the microscopic arrangement of fluxlines. Direct imaging [5] and decoration techniques [6] all have inherent drawbacks, and muon spin rotation has not yet achieved the sophistication to resolve the most subtle effects [7]. By comparison, small angle neutron scattering (SANS) provides unrivalled insights into the crystallography of the FLL, and is the only technique capable of unequivocably resolving such questions.The demanding nature of neutron experiments requires large single crystals (masses > ∼ 200mg), and because of this YBa 2 Cu 3 O 7−δ (YBCO) has been the cuprate of choice for SANS experiments [8]. However, the materials properties of YBCO are complicated. The presence of Cu-O chains which are aligned with the crystallographic b direction render the otherwise tetragonal structure orthorhombic. Upon cooling from the growth, twin boundaries form along {110} directions separating domains of interchanged a and b axes. A strong interaction between flux-lines and these twin planes significantly influences FLL properties. There is a further effect of the chains. Although the orthorhombic distortion is only slight (≈ 1%), the electronic structure is markedly affected, and the consequence is anisotropy within the abplane of both superconducting [9,10] and normal state [11] properties. All previous SANS studies have been on heavily twinned crystals [12,13], and although observations of a pattern with four-fold symmetry were claimed to be due to unconventional d x 2 −y 2 pairing [12], it could not be discounted that alignment by twin planes, in comb...

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confidence: 71%

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
12
46
0
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“…The frequency dependence is almost linear up to 1 eV and the slopes are nearly the same for all samples. This linear frequency dependence has been observed in many other correlated systems, [6,19] however, there is still no concrete explanation for this behavior. Within the GBR picture for the Mott transition, the spectral weight of the QP peak, ω * 2 p , is an order parameter and should be proportional to 1/m * .…”

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confidence: 95%

Spectral Evolution in(Ca,Sr)RuO3near the Mott-Hubbard Transition

et al. 1999

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We investigated the optical properties of (Ca,Sr)RuO3 films on the borderline of a metal-insulator (M-I) transition. Our results show all of the predicted characteristics for a metallic Mott-Hubbard system, including (i) a mass enhancement in dc-limit, (ii) an U/2 excitation, and (iii) an U excitation. Also, a self-consistency is found within the Gutzwiller-Brinkman-Rice picture for the Mott transition. Our finding displays that electron correlation should be important even in 4d materials.PACS numbers: 71.30.+h, 71.27.+a, 71.10.Fd, Correlation between electrons in transition and rare earth metal compounds has attracted lots of attentions. In general, the more localized the electron wave function is, the stronger the correlation effects are. As a result, correlation effects are believed to be much more important in describing 3d electrons than 4d or 5d electrons.A metal-insulator (M-I) transition driven by electron correlation was proposed by Mott and subsequently investigated intensively.[1] Since the Hubbard model was proposed in early 1960's, it has been widely accepted as the simplest model which can describe correlation effects. Although the model is composed of only two parameters, i.e. inter-site hopping energy t (= W/z) and on-site Coulomb repulsive energy U , it has not been exactly solved yet except for one dimensional case. [W and z are the bandwidth and the coordination number, respectively.] Up to several years ago, different approaches provided limited insights into different aspects of the M-I transition. However, recent theoretical progresses, including a slave-boson approach, infinite dimension limit approaches with several techniques, and numerical calculations for finite size systems, started to provide a coherent picture. [2] According to the traditional Gutzwiller-BrinkmanRice (GBR) picture, [3] the Mott M-I transition from a metallic side can be described by narrowing and disappearing of a Fermi liquid quasi-particle (QP) band at a critical value of correlation strength, (U/W ) c . Under this strong renormalization, an effective mass, m * , [4] of the QP is related by:Recent theoretical works predict that one particle spectral function A(ω) for the metallic phase will be split into lower (LHB) and upper (UHB) Hubbard bands, in addition to the QP band located at zero frequency. Fig. 1(a) shows the schematic diagram of A(ω). Then, the corresponding optical conductivity spectra σ 1 (ω) can be easily predicted and displayed in Fig. 1(b). Note that σ 1 (ω) in a metallic side has three pronounced features: (i) a "QP peak" near zero frequency, (ii) an "U/2 peak" due to optical transitions between QP band and LHB (or UHB), and (iii) an "U peak" due to a transition between LHB and UHB.FIG. 1. Schematic diagrams of (a) one particle spectral function and (b) optical conductivity, for 4/6-filled metallic Mott-Hubbard system. Dotted lines indicate the contributions from O(2p) band.In this letter, we will report optical properties of (Ca,Sr)RuO 3 films, where four electrons occupy triply degenerate t 2g...

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“…Some authors argue that it may be understood in terms of quasiparticles scattered by a frequency and temperature dependent scattering rate 2,5,6 ; others that it should be understood in more exotic terms 7,8 . Recently, the issue of the adequacy of a quasiparticle-only description has been reexamined 9 .…”

Section: Introductionmentioning

confidence: 99%

Mott physics and the optical conductivity of electron-doped cuprates

et al. 2005

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The doping and temperature dependent conductivity of electron-doped cuprates is analysed. The variation of kinetic energy with doping is shown to imply that the materials are approximately as strongly correlated as the hole-doped materials. The optical spectrum is fit to a quasiparticle scattering model; while the model fits the optical data well, gross inconsistencies with photoemission data are found, implying the presence of a large, strongly doping dependent Landau parameter.

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Superconducting energy gap and normal-state conductivity of a single-domainYBa2Cu3

Cited by 444 publications

References 18 publications

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
12
46
0
View full text Add to dashboard Cite

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
12
46
0
View full text Add to dashboard Cite

Spectral Evolution in(Ca,Sr)RuO3near the Mott-Hubbard Transition

Mott physics and the optical conductivity of electron-doped cuprates

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Superconducting energy gap and normal-state conductivity of a single-domainYBa2Cu3

Cited by 444 publications

References 18 publications

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δJohnson1, Forgan2, Lloyd3 et al. 1999Phys. Rev. Lett.5012460View full textAdd to dashboardCite

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δJohnson1, Forgan2, Lloyd3 et al. 1999Phys. Rev. Lett.5012460View full textAdd to dashboardCite

Spectral Evolution in(Ca,Sr)RuO3near the Mott-Hubbard Transition

Mott physics and the optical conductivity of electron-doped cuprates

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Product

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About

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
12
46
0
View full text Add to dashboard Cite

Flux-Line Lattice Structures in UntwinnedYBa2Cu3O7−δ
Johnson
¹
,
Forgan
²
,
Lloyd
³

et al. 1999
Phys. Rev. Lett.
50
12
46
0
View full text Add to dashboard Cite