Superconductivity-Induced Transfer of In-Plane Spectral Weight in Bi
 2
 Sr
 2
 CaCu
 2
 O
 8+δ

Molegraaf, Hajo; Presura, C.; Marel, D. van der; Kes, P.H.; Li, M.

doi:10.1126/science.1069947

Cited by 316 publications

(423 citation statements)

References 29 publications

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“…Much discussion has been raised by the question of "kinetic energy driven superconductivity" where, in contrast to BCS, the energy gain arises from a decrease in kinetic energy. The reported gain of kinetic energy ∆E kin ≈ 0.5 − 1.0 meV on the basis of optical spectroscopy at optimal doping [25,26] corresponds well to our result (∆E kin ≈ 1.1 meV), but we have to be aware that the use of a low-energy cut-off in the frequency-integration of the conductivity is not unambiguous. Good agreement with experiment is also found for the strong antiferromagnetic correlations in the superconducting phase.…”

supporting

confidence: 88%

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

Eichenberger

Baeriswyl

2007

Phys. Rev. B

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A variational ground state of the repulsive Hubbard model on a square lattice is investigated numerically for an intermediate coupling strength (U = 8t) and for moderate sizes (from 6 × 6 to 10 × 10). Our ansatz is clearly superior to other widely used variational wave functions. The results for order parameters and correlation functions provide new insight for the antiferromagnetic state at half filling as well as strong evidence for a superconducting phase away from half filling.PACS numbers: 71.10. Fd,74.20.Mn, The Hubbard model plays a key role in the analysis of correlated electron systems, and it is widely used for describing quantum antiferromagnetism, the Mott metalinsulator transition and, ever since Anderson's suggestion [1], superconductivity in the layered cuprates. Several approximate techniques have been developed to determine the various phases of the two-dimensional Hubbard model. For very weak coupling, the perturbative Renormalization Group extracts the dominant instabilities in an unbiased way, namely antiferromagnetism at half filling and d-wave superconductivity for moderate doping [2,3]. Quantum Monte Carlo simulations have been successful in extracting the antiferromagnetic correlations at half filling [4,5], but in the presence of holes the numerical procedure is plagued by the fermionic minus sign problem [6]. This problem appears to be less severe in dynamic cluster Monte Carlo simulations, which exhibit a clear tendency towards d-wave superconductivity for intermediate values of U [7].Variational techniques address directly the ground state and thus offer an alternative to quantum Monte Carlo simulations, which are limited to relatively high temperatures. Previous variational wave functions include mean-field trial states from which configurations with doubly occupied sites are either completely eliminated (full Gutzwiller projection) [8,9,10] or at least partially suppressed [11]. Recently, more sophisticated wave functions have been proposed, which include, besides the Gutzwiller projector, non-local operators related to charge and spin densities [12,13]. Our own variational wave function is based on the idea that for intermediate values of U the best ground state is a compromise between the conflicting requirements of low potential energy (small double occupancy) and low kinetic energy (delocalization). It is known that the addition of an operator involving the kinetic energy yields an order of magnitude improvement of the ground state energy with respect to a wave function with a Gutzwiller projector alone [14]. In this letter, we show that such an additional term allows us to draw an appealing picture of the ground state, both at half filling and as a function of doping (some preliminary results have been published [15,16]).In its most simple form, the 2D Hubbard model is composed of two terms,Ĥ = tT + UD , witĥHere c † iσ creates an electron at site i with spin σ, the summation is restricted to nearest-neighbor sites and n iσ = c † iσ c iσ . We consider a square lattice with peri...

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confidence: 88%

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

Eichenberger

Baeriswyl

2007

Phys. Rev. B

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“…(17)), making use of Eq. (16). 12 For some pertinent details we refer the reader to an extensive analysis of the large-r asymptotic behaviour of ̺σ(r) pertaining to uniform and isotropic GSs in appendix J of [78].…”

Section: Equations Determining the Fermi Surfaces Of Uniform Metallicmentioning

confidence: 99%

“…It follows therefore that the FL metallic states of Coulomb-interacting fermions fall into the category of systems dealt with in this Section. 16 16 From the defining expression in Eq. (25) and the fact that η k;σ ∼ 0 for k → kf;σ ∈ Sf;σ (the latter rendering an assumption with regard to the boundedness of ∇ k nσ(k) for k → kf;σ redundant) it follows that a possible (logarithmic) divergence of ∇ k ϑ k;σ for k → kf;σ directly implies an analogous divergence of ∇ k η k;σ for k → kf;σ.…”

Section: < τ = γ ≤ 1 (Includes Fermi Liquids)mentioning

confidence: 99%

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On the (anisotropic) uniform metallic ground states of fermions interacting through arbitrary two-body potentials inddimensions

Farid¹

2004

Philosophical Magazine

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We demonstrate that the skeleton of the Fermi surface Sf;σ pertaining to a uniform metallic ground state (corresponding to fermions with spin index σ) is determined by the Hartree-Fock contribution Σ hf σ (k) to the dynamic self-energy Σσ(k; ε). That is to say, in order for k ∈ Sf;σ, it is necessary (but for anisotropic ground states in general not sufficient) that the following equation be satisfied:where ε k stands for the underlying non-interacting energy dispersion and εf for the exact interacting Fermi energy. The Fermi surface Sf;σ consists of the set of k points which in addition to satisfying the above equation fulfilwhereThe set of k points which satisfy the first of the above two equations but fail to satisfy the second constitute the pseudogap region of the putative Fermi surface of the interacting system. We consider the behaviour of the ground-state momentum-distribution function nσ(k) for k in the vicinity of Sf;σ and show that, whereas for the uniform metallic ground states of the conventional single-band Hubbard Hamiltonian, described in terms of an on-site interaction, nσ(k − f;σ ) ≥ 1 2 and nσ(k + f;σ ) ≤ 1 2 (here k − f;σ and k + f;σ denote vectors infinitesimally close to Sf;σ, located respectively inside and outside the underlying Fermi sea), for interactions of non-zero range these inequalities can be violated (without thereby contravening the stability condition nσ(k − f;σ ) ≥ nσ(k + f;σ )). This aspect is borne out by the nσ(k) pertaining to the normal states of for instance liquid 3 He (corresponding to a range of applied pressure) as determined by means of quantum Monte Carlo calculations. We further demonstrate that for Fermi-liquid metallic states of fermions interacting through interaction potentials of non-zero range (e.g. the Coulomb potential), the zero-temperature limit of nσ(k) does not need to be equal to 1 2 for k ∈ Sf;σ; this in strict contrast with the uniform Fermi-liquid metallic states of the single-band Hubbard Hamiltonian (if such states at all exist). This aspect should be taken into account while analyzing the nσ(k) deduced from the angle-resolved photoemission data concerning real materials. We discuss, in the light of the findings of the present work, the growing experimental evidence with regard to the 'frustration' of the kinetic energy of the charge carriers in the normal states of the copper-oxide-based high-temperature superconducting compounds.

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“…The data from [79] HTSC oxides was studied in [79] and [75], by assuming that "intraband" effects are exhausted for ω c ≈ 1.25 eV and the main temperature dependence of the high-frequency region comes for α = 2 in Eq. (22), i.e.…”

Section: Dynamical Conductivity σ (ω)mentioning

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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Superconductivity-Induced Transfer of In-Plane Spectral Weight in Bi ₂ Sr ₂ CaCu ₂ O _8+δ

Cited by 316 publications

References 29 publications

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

On the (anisotropic) uniform metallic ground states of fermions interacting through arbitrary two-body potentials inddimensions

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

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Superconductivity-Induced Transfer of In-Plane Spectral Weight in Bi 2 Sr 2 CaCu 2 O 8+δ

Cited by 316 publications

References 29 publications

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: A variational study

On the (anisotropic) uniform metallic ground states of fermions interacting through arbitrary two-body potentials inddimensions

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

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Superconductivity-Induced Transfer of In-Plane Spectral Weight in Bi ₂ Sr ₂ CaCu ₂ O _8+δ