Transport studies of La1.92Sr0.08Cu1-xMxO4 (M=Ni and Zn) and Nd2-yCeyCuO4 up to about 900 K

Takeda, Jun; Nishikawa, Takashi; Sato, M.

doi:10.1016/0921-4534(94)90635-1

Cited by 100 publications

(97 citation statements)

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“…This indicates that NCCO is probably not a "real" n-type cuprate, and its stripons are also based on holon states, where the extra doped negative charge occupies another QE band. The Hall constant in NCCO [18] is consistent with Fig. 1(d), and our prediction that the sign of both n p H and n q H is determined by the bare QE states (and changes in NCCO with doping).…”

supporting

confidence: 90%

“…The ω dependencies (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) derived in the auxiliary space remain valid in the physical space, both for the coherent bands, and for the incoherent background, detected, e.g., in ARPES results. The present results for Γ q (13) are reflected in the observed non-Fermi-liquid bandwidths, having a ∝ ω and a constant term.…”

mentioning

confidence: 91%

“…TEP results for NCCO [18] show that in superconducting doping levels it has the same behavior as in p-type cuprates [ Fig. 1(a)], but with an opposite effect of doping.…”

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confidence: 94%

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Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

Ashkenazi

2002

Journal of Physics and Chemistry of Solids

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Abstract-The quasiparticles of the high-Tc cuprates are found to consist of: polaronlike "stripons" carrying charge, and associated primarily with large-U orbitals in stripe-like inhomogeneities; "quasi-electrons" carrying charge and spin, and associated with hybridized small-U and large-U orbitals; and "svivons" carrying spin and lattice distortion. It is shown that this electronic structure leads to the systematic behavior of spectroscopic and transport properties of the cuprates. High-Tc pairing results from transitions between pair states of stripons and quasi-electrons through the exchange of svivons. The cuprates fall in the regime of crossover between BCS and preformed-pairs Bose-Einstein condensation behaviors.First-principles calculations in the cuprates support an approach based on the existence of both "large-U " and "small-U " orbitals in the vicinity of the Fermi level (E F ). Let us denote the fermion creation operator of a small-U electron in band ν, spin σ (which can be assigned a number ±1), and wave vector k by c † νσ (k). The large-U orbitals in the CuO 2 planes are approached through the "slavefermion" method [1]. A large-U electron in site i and spin σ is then created by d † iσ = e † i s i,−σ , if it is in the "upper-Hubbard-band", and by dif it is in a Zhang-Rice-type "lower-Hubbard-band". Here e i and h i are ("excession" and "holon") fermion operators, and s iσ are ("spinon") boson operators. These auxiliary particles have to satisfy the constraint:Within the "auxiliary space" a chemicalpotential-like Lagrange multiplier is introduced to impose the constraint on the average. Physical observables are calculated as combinations of Green's functions of the auxiliary space. Since the time evolution of Green's functions is determined by the Hamiltonian which obeys the constraint rigorously, it is not expected to be violated as long as the approximations used for these Green's functions are justifiable.The spinon states are diagonalized by applying the Bogoliubov transformation [2]:The Bose operators ζ † σ (k) create spinon states of "bare" energies ǫ ζ (k) which have a V-shape zero minimum at k = k 0 . Bose condensation results in antiferromagnetic (AF) order at wave vector

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Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

Ashkenazi

2002

Journal of Physics and Chemistry of Solids

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“…For example, |R H | increases as the temperature decreases below T 0 ∼ 700K, and |R H | ≫ 1/ne (n being the electron filling number) at lower temperatures [24]. The sign of R H is positive in hole-doped systems like YBa 2 Cu 3 O 7−δ (YBCO) and La 2−δ Sr δ CuO 4 (LSCO), whereas it is negative in electron-doped systems like Nd 2−δ Ce δ CuO 4 (NCCO), although their Fermi surfaces (FS's) observed in ARPES measurements are hole-like [25].…”

Section: Continuity and Exact Solutionmentioning

confidence: 99%

From Kondo Effect to Fermi Liquid

Kontani

Yamada

2005

J. Phys. Soc. Jpn.

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The Kondo effect has been playing an important role in strongly correlated electon systems. The important point is that the magnetic impurity in metals is a typical example of the Fermi liquid. In the system the local spin is conserved in the ground state and continuity with respect to Coulomb repulsion U is satisfied. This nature is satisfied also in the periodic systems as far as the systems remain as the Fermi liquid. This property of the Fermi liquid is essential to understand the cuprate high-Tc superconductors (HTSC). On the basis of the Fermi liquid theory we develop the transport theory such as the resistivity and the Hall coefficient in strongly correlated electron systems, such as HTSC, organic metals and heavy Fermion systems. The significant role of the vertex corrections for total charge-and heat-currents on the transport phenomena is explained. By taking the effect of the current vertex corrections into account, various typical non-Fermi-liquid-like transport phenomena in systems with strong magnetic and/or superconducting flucutations are explained within the Fermi liquid theory. 1.IntroductionSince the discovery of Kondo Effect, the theory of electron correlation has been developed remarkably. In particular, the study of the strongly correlated electron systems such as cuprates and heavy fermions is actively performed. In this article we discuss the contribution of Kondo theory to the theory of strongly correlated electron systems. The key word is the singlet: The ground state of the single impurity in metals is the singlet where a localized spin is coupled antiferromagnetically with conduction electron spin. The resonating-valence-bond (RVB) state is a spin singlet state and is considered to be the basis of the cuprate high-T c superconductivity (HTSC). By using Anderson's orthogonality theorem, we show that the Fermi liquid state is nothing but the RVB state in metal. As a result, we can reasonably arrive at the pairing theory of superconductivity. Anderson HamiltonianIn 1961 Anderson presented the following Hamiltonian and explained the appearance of a localized moment in metals by using the Hartree-Fock approximation.[1]The first term is the energy of conduction electrons and the third term is the d-electron part. The last term is the Coulomb repulsion between two d-electrons and is the only many-body interaction. The symmetric Anderson Hamiltonian possesses the electron-hole symmetry and is easy to understand the physical meaning because of the suppressed charge fluctuations. By assuming the average number of d-electrons is unity and taking the nonmagnetic case (< n dσ >=< n d−σ >= 1/2) ,where E Here ρ is the density of states of conduction electrons at the Fermi energy. Hereafter, we assume the band-width of conduction band is infinite and ρ is constant. 2-1. Kondo effectAnderson explained the existence of magnetic moment as the effect of electron correlation. However, there existed a long standing mystery for these 30 years.[2] As shown in Fig.1, when we decrease the temperature, the resid...

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“…While R H does not exhibit any correlation with y, the behavior changes systematically with T c , which resembles to that of high T c Cu Oxides. [10][11][12] If the magnetic fluctuation is relevant to the observed strong T dependence of R H as in Cu oxides, the fact that the characteristic temperature of the R H -T curves is smaller by a factor of 2 than that of Cu oxides is important for the consideration of T c value. Figure 4 shows NMR Knight shift of 75 As reported in our previous paper 5) Here, combining our new data taken up to ~250K for 75 As and those of 19 F, 13) we estimate the chemical shift of 75 As by the method shown in the inset and indicate it by the grey broken line.…”

Section: Resultsmentioning

confidence: 99%

Studies of the Superconductivity of LaFe_1-yCo_yAsO_1-xF_x(x=0.11) –Impurity Effect and NMR Knight Shift–

et al. 2008

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LaFe 1-y Co y AsO 1-x F x (x=0.11) with various y values were prepared and their electrical resistivities, superconducting diamagnetisms and Hall coefficients have been measured. 75 Asand 135La-NMR studies have also been carried out In spite of the successful Co-doping, we have not found any meaningful correlation of T c with y, which indicates that the T c -suppression by Co-doping is considered not to be so significant as expected for superconductors with nodes. Even for superconductors without nodes, it may not be easy to expect this small effect on T c , if there are two different (disconnected) Fermi surfaces whose order parameters have opposite signs. The data of the NMR Knight shift indicate that the Cooper pairs are in the singlet state and the spin susceptibility is almost fully suppressed at low temperature.

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Transport studies of La1.92Sr0.08Cu1-xMxO4 (M=Ni and Zn) and Nd2-yCeyCuO4 up to about 900 K

Cited by 100 publications

References 11 publications

Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

From Kondo Effect to Fermi Liquid

Studies of the Superconductivity of LaFe_1-yCo_yAsO_1-xF_x(x=0.11) –Impurity Effect and NMR Knight Shift–

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Transport studies of La1.92Sr0.08Cu1-xMxO4 (M=Ni and Zn) and Nd2-yCeyCuO4 up to about 900 K

Cited by 100 publications

References 11 publications

Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

Stripe fluctuations, carriers, spectroscopies, transport, and BCS–BEC crossover in the high-Tc cuprates

From Kondo Effect to Fermi Liquid

Studies of the Superconductivity of LaFe1-yCoyAsO1-xFx(x=0.11) –Impurity Effect and NMR Knight Shift–

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Studies of the Superconductivity of LaFe_1-yCo_yAsO_1-xF_x(x=0.11) –Impurity Effect and NMR Knight Shift–