Magnetic correlations in high temperature superconductivity

Kampf, Arno P.

doi:10.1016/0370-1573(94)90120-1

Cited by 235 publications

(241 citation statements)

References 452 publications

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“…One can see from Fig.1(a) that the antinodal kink appears in some range of parameters t p and α, such as t p = 2.0J and α = 0.43. The RPA correction factor α = 0.34, 0.43 and 0.55 correspond to the critical doping density of the AF instability δ c = 0.02, 0.05 and 0.09, while δ c = 0.02 ∼ 0.05 is within the experimental range [15]. Meanwhile, the ARPES experiment indicated that t ⊥,exp (corresponding to δt p , δ ∼ 0.2) is 44 ± 5meV [17], i.e., t p = 1.6 ∼ 2.0J here.…”

Section: Pacs Numbersmentioning

confidence: 57%

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Theoretical investigation of the quasiparticle dispersion of bilayer high-Tcsuperconductors

Zhou

Wang

2005

Phys. Rev. B

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The renormalization of quasiparticle (QP) dispersion in bilayer high-Tc cuprates is investigated theoretically by examining respectively the interactions of the QP with spin fluctuations (SF) and phonons. It is illustrated that both interactions are able to give rise to a kink in the dispersion around the antinodes (near (π, 0)). However, remarkable differences between the two cases are found for the peak/dip/hump structure in the lineshape, the QP weight, and the interlayer coupling effect on the kink, which are suggested to serve as a discriminance to single out the dominant interaction in the superconducting state. A comparison to recent photoemission experiments shows clearly that the coupling to the spin resonance is dominant for the QP around antinodes in bilayer systems.

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Section: Pacs Numbersmentioning

confidence: 57%

“…, with ω 0 the pole of G. The parameters we choose are t = 2J, t ′ = −0.7t, J = 120 meV and J ⊥ = 0.1J [15]. Except in Fig.4, the doping density is set at δ = 0.2.…”

Section: Pacs Numbersmentioning

confidence: 99%

Theoretical investigation of the quasiparticle dispersion of bilayer high-Tcsuperconductors

Zhou

Wang

2005

Phys. Rev. B

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“…The resulting 2D Néel state with decoupled (a,b) planes along the c direction is the well-known classical ground state of the high-T c superconductors La 2 CuO 4 and YBa 2 Cu 3 O 6 . 61 In contrast, if E z Ͻ0 and ͉E z ͉ is large, ͉E z ͉/Jӷ1, then i ϭ0 in Eq. ͑3.2͒, and the holes occupy ͉z͘ orbitals.…”

Section: A Anisotropy Of Antiferromagnetic Interactionsmentioning

confidence: 98%

Quantum melting of magnetic long-range order near orbital degeneracy: Classical phases and Gaussian fluctuations

2000

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We address the role played by orbital degeneracy in strongly correlated transition-metal compounds. Specifically, we study the effective spin-orbital model derived for the d 9 ions in a three-dimensional perovskite lattice, as in KCuF 3 , where at each site the doubly degenerate e g orbitals contain a single hole. The model describes the superexchange interactions that depend on the pattern of orbitals occupied and shows a nontrivial coupling between spin and orbital variables at nearest-neighbor sites. We present the ground-state properties of this model, depending on the splitting between the e g orbitals E z , and the Hund's rule coupling in the excited d 8 states, J H . The classical phase diagram consists of six magnetic phases which all have different orbital ordering: two antiferromagnetic ͑AF͒ phases with G-AF order and either x 2 Ϫy 2 or 3z 2 Ϫr 2 orbitals occupied, two phases with mixed orbital ͑MO͒ patterns and A-AF order, and two other MO phases with either C-AF or G-AF order. All of them become degenerate at the multicritical point M ϵ(E z ,J H )ϭ(0,0). Using a generalization of linear spin-wave theory we study both the transverse excitations which are spin waves and spin-andorbital waves, as well as the longitudinal ͑orbital͒ excitations. The transverse modes couple to each other, providing a possibility of measuring the new spin-and-orbital excitations in inelastic neutron spectroscopy. As the latter excitation turns into a soft mode near the M point, quantum corrections to the long-range-order parameter are drastically increased near the orbital degeneracy, and classical order is suppressed in a crossover regime between the G-AF and A-AF phases in the (E z ,J H ) plane. This behavior is reminiscent of that found in frustrated spin models, and we conclude that orbital degeneracy provides a different and physically realizable mechanism which stabilizes a spin liquid ground state due to inherent frustration of magnetic interactions. We also point out that such a disordered magnetic phase is likely to be realized at low J H and low electronphonon coupling, as in LiNiO 2 . I. NOVEL MECHANISM OF FRUSTRATION NEAR ORBITAL DEGENERACYQuite generally, strongly correlated electron systems involve orbitally degenerate states, 1 such as 3d(4d) states in transition metal compounds, and 4 f (5 f ) states in rare-earth compounds. Yet, the orbital degrees of freedom are ignored in most situations and the common approach is to consider a single correlated orbital per atom which leads to spin degeneracy alone. Indeed, most of the current studies of strongly correlated electrons deal with models of nondegenerate orbitals. The problems discussed recently include mechanisms of ferromagnetism in the Hubbard model, 2 hole propagation and quasiparticles in the t-J model, 3 and magnetic states of the Kondo lattice.4 Of course, in many actually existing compounds the orbital degeneracy is removed by the crystal field, and a single-orbital approach is valid per se. Also, from a fundamental point of view it is often possible ...

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“…It turns out that the case U >> t is realized, since ∆ pd ≫ t = t 2 pd /∆ pd . The effective and minimal Hamiltonian which describes the low-energy physics of HTSC oxides comprises also the long-range Coulomb interactionV C and the EPIV EPI -see [7], [2] …”

Section: Theory Of Strong Electronic Correlationsmentioning

confidence: 99%

Electron-Phonon Interaction and Strong Correlations in High-Temperature Superconductors: One can not avoid the unavoidable

Kulić¹

2004

AIP Conference Proceedings

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Abstract. The important role of the electron-phonon interaction (EPI) in explaining the properties of the normal state and pairing mechanism in high-T c superconductors (HTSC) is discussed. A number of experimental results are analyzed such as: dynamical conductivity, Raman scattering, neutron scattering, ARPES, tunnelling measurements, isotope effect and etc. They give convincing evidence that the EPI is strong and dominantly contributes to pairing in HTSC oxides. It is argued that strong electronic correlations in conjunction with the pronounced (in relatively weakly screened materials) EPI are unavoidable ingredients for the microscopic theory of pairing in HTSC oxides. I present the well defined and controllable theory of strong correlations and the EPI. It is shown that strong correlations give rise to the pronounced forward scattering peak in the EPI -the FSP theory. The FSP theory explains in a consistent way several (crucial) puzzles such as much smaller transport coupling constant than the pairing one (λ tr ≪ λ ), which are present if one interprets the results in HTSC oxides by the old Migdal-Eliashberg theory for the EPI. The ARPES shift puzzle where the nodal kink at 70 meV is unshifted in the superconducting state, while the anti-nodal one at 40 meV is shifted can be explained at present only by the FSP theory. A number of other interesting predictions of the FSP theory are also discussed.

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Magnetic correlations in high temperature superconductivity

Cited by 235 publications

References 452 publications

Theoretical investigation of the quasiparticle dispersion of bilayer high-Tcsuperconductors

Theoretical investigation of the quasiparticle dispersion of bilayer high-Tcsuperconductors

Quantum melting of magnetic long-range order near orbital degeneracy: Classical phases and Gaussian fluctuations

Electron-Phonon Interaction and Strong Correlations in High-Temperature Superconductors: One can not avoid the unavoidable

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