Electronic states of doped holes and magnetic properties in La2−xMxCuO4 (M = Sr, Ba)

Oda, Masahiro; Nakano, Tohru; Kamada, Y.; Ido, M.

doi:10.1016/0921-4534(91)90567-i

Cited by 58 publications

(43 citation statements)

References 16 publications

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“…The functional form of χ 2D ðx;TÞ is that of a 2D Heisenberg antiferromagnet. Above x ∼ 0.19, there is an anomalous occurrence of Curie paramagnetism, such that χðx;TÞ ¼ χ 0 ðxÞ þ χ 2D ðx;TÞ þ CðxÞ T ; [5] where the Curie constant CðxÞ increases with increased doping (10,13,14), but subsequently decreases (10, 22) above x ∼ 0.26 (i.e., beyond the superconducting phase). The onset of the Curie term is accompanied by a saturation of the superfluid density in the superconducting phase (23) and a monotonic increase in the width of the internal magnetic field distribution with increasing hole doping in an external field at temperatures above T c (24).…”

Section: Resultsmentioning

confidence: 99%

“…However, the recent proposal by Kopp et al (8) that ferromagnetic (FM) fluctuations compete with d-wave superconductivity is a challenge to the notion that overdoped copper oxides strictly conform to such conventional wisdom. The primary motivation for their hypothesis is a strong upturn in the magnetic susceptibility immediately above T c for doping levels greater than p ∼ 0.19 (9)(10)(11)(12)(13)(14). A tendency toward FM order for high charge doping ( Fig.…”

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confidence: 99%

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Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Sonier

Kaiser

Pacradouni

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The doping of charge carriers into the CuO 2 planes of copper oxide Mott insulators causes a gradual destruction of antiferromagnetism and the emergence of high-temperature superconductivity. Optimal superconductivity is achieved at a doping concentration p beyond which further increases in doping cause a weakening and eventual disappearance of superconductivity. A potential explanation for this demise is that ferromagnetic fluctuations compete with superconductivity in the overdoped regime. In this case, a ferromagnetic phase at very low temperatures is predicted to exist beyond the doping concentration at which superconductivity disappears. Here we report on a direct examination of this scenario in overdoped La 2−x Sr x CuO 4 using the technique of muon spin relaxation. We detect the onset of static magnetic moments of electronic origin at low temperature in the heavily overdoped nonsuperconducting region. However, the magnetism does not exist in a commensurate long-range ordered state. Instead it appears as a dilute concentration of static magnetic moments. This finding places severe restrictions on the form of ferromagnetism that may exist in the overdoped regime. Although an extrinsic impurity cannot be absolutely ruled out as the source of the magnetism that does occur, the results presented here lend support to electronic band calculations that predict the occurrence of weak localized ferromagnetism at high doping.A ttempts within the framework of standard theories have failed to explain how high-temperature superconductivity emerges from charge carrier doping of an antiferromagnetic (AF) Mott insulator (1). The conventional Bardeen-CooperSchrieffer (BCS) theory of low-temperature superconductors (2) assumes that above the critical transition temperature (T c ) the electrons form a Landau Fermi liquid, and that superconductivity arises from pair condensation of the associated low-energy excitations (quasiparticles). What is clear in the case of copper oxides is that over the initial doping range where superconductivity first appears, ordinary Landau Fermi liquid theory does not apply. This realization has prompted theories in which the properties of the ordinary Fermi liquid are hidden (3), or alternatively only some properties of the Fermi liquid persist (4).A BCS-type theory may be applicable in the heavily overdoped region, where an ordinary Fermi liquid is observed (5-7). However, the recent proposal by Kopp et al. (8) that ferromagnetic (FM) fluctuations compete with d-wave superconductivity is a challenge to the notion that overdoped copper oxides strictly conform to such conventional wisdom. The primary motivation for their hypothesis is a strong upturn in the magnetic susceptibility immediately above T c for doping levels greater than p ∼ 0.19 (9-14). A tendency toward FM order for high charge doping (Fig. 1) is supported by electronic band calculations for super cells of La 2−x Ba x CuO 4 (15). However, these calculations favor the appearance of weak ferromagnetism about concentrated regions of ...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Sonier

Kaiser

Pacradouni

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…In underdoped cuprates, the susceptibility above T N can be scaled into a universal form [179]. For overdoped cuprates, this same form holds, if a CurieWeiss term is first subtracted off [756]. In LSCO and LBCO, the Curie constant grows linearly in x − x V HS , where x V HS is the doping of optimal T c , up to x ≃ 0.26.…”

Section: Susceptibilitymentioning

confidence: 99%

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Markiewicz

1997

Journal of Physics and Chemistry of Solids

371

280

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The Van Hove singularity (VHS) provides a paradigm for the study of the role of peaks in the density of states (dos) on electronic properties. More importantly, it appears to play a major role in the physics of the high-Tc superconductors, particularly since recent photoemission studies have found that the VHS is close to the Fermi level in most of the high-Tc cuprates near the composition of optimum Tc. This paper offers a comprehensive survey of the VHS model, describing both theoretical properties and experimental evidence for the picture. Special topics discussed include a survey of the Fermi surfaces of the cuprates and related compounds, and an analysis of the reliability of the slave boson approach to correlation effects. While many properties of the cuprates can be qualitatively understood by a simple rigid-band-filling model, this is inadequate for more quantitative results, since correlation effects tend to pin the Fermi level near the VHS over an extended doping range, and can lead to a nanoscale phase separation. Furthermore, the peaks in the dos lead to competition from other instabilities, both magnetic and structural (related to charge density waves). A novel form of dynamic structural instability, involving dynamic VHS-Jahn-Teller effects has been predicted. Scattered through the literature, there is considerable experimental evidence for both nanoscale phase separation of holes, and for local, possibly dynamic, structural disorder. This review attempts to gather these results into a comprehensive database, to sort the results, and to see how they fit into the Van Hove scenario. Recent experiments on underdoped cuprates are found to provide a strong confirmation that the pseudogap is driven by a splitting of the VHS degeneracy.

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“…2. In both cases, the upturn becomes more pronounced with overdoping (14)(15)(16)(17)(18)(19). Despite motivated effort, it has not been possible to attribute this unusual behavior to Curie susceptibility of a magnetic impurity phase.…”

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confidence: 98%

Competing ferromagnetism in high-temperature copper oxide superconductors

Kopp

Ghosal

Chakravarty

2007

Proc. Natl. Acad. Sci. U.S.A.

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The extreme variability of observables across the phase diagram of the cuprate high-temperature superconductors has remained a profound mystery, with no convincing explanation for the superconducting dome. Although much attention has been paid to the underdoped regime of the hole-doped cuprates because of its proximity to a complex Mott insulating phase, little attention has been paid to the overdoped regime. Experiments are beginning to reveal that the phenomenology of the overdoped regime is just as puzzling. For example, the electrons appear to form a Landau Fermi liquid, but this interpretation is problematic; any trace of Mott phenomena, as signified by incommensurate antiferromagnetic fluctuations, is absent, and the uniform spin susceptibility shows a ferromagnetic upturn. Here, we show and justify that many of these puzzles can be resolved if we assume that competing ferromagnetic fluctuations are simultaneously present with superconductivity, and the termination of the superconducting dome in the overdoped regime marks a quantum critical point beyond which there should be a genuine ferromagnetic phase at zero temperature. We propose experiments and make predictions to test our theory and suggest that an effort must be mounted to elucidate the nature of the overdoped regime, if the problem of high-temperature superconductivity is to be solved. Our approach places competing order as the root of the complexity of the cuprate phase diagram.quantum-phase transition ͉ non-Fermi liquid ͉ broken symmetry ͉ quantum order ͉ criticality T he superconducting dome (see Fig. 1), that is, the shape of the superconducting transition temperature T c as a function of doping (added charge carriers), x, is a clue that the high-T c superconductors are unconventional. Conventional superconductors, explained so beautifully by Bardeen, Cooper, and Schrieffer (52), have a unique ground state that is not naturally separated by any nonsuperconducting states. The electronphonon mechanism leads to superconductivity for arbitrarily weak attraction between electrons. To destroy a superconducting state requires a magnetic field or strong material disorder. In the absence of disorder or magnetic field, it is difficult to explain the sharp cutoffs at x 1 and x 2 within the Bardeen, Cooper, and Schrieffer theory. For high-T c superconductors, there is considerable evidence that competing order parameters are the underlying reason. Thus, x 1 and x 2 signify quantum phase transitions, most likely quantum critical points (QCPs) (1). Understanding high-T c superconductors therefore requires an understanding of possible competing orders (2, 3). The QCP at x 1 has been extensively studied (4-8), but little is known about x 2 . Recent work has also emphasized the importance of the maximum of the uniform susceptibility in defining the pseudogap line T* in Fig. 1 that ends at another QCP at x c (8). Here, we attempt, instead, at gaining insight from the possible existence of a QCP at x 2 .Complex materials (cuprates, heavy fermions, and organics)...

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Electronic states of doped holes and magnetic properties in La2−xMxCuO4 (M = Sr, Ba)

Cited by 58 publications

References 16 publications

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Competing ferromagnetism in high-temperature copper oxide superconductors

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