Absence of magnetic order in (Ba, K)BiO3

Uemura, Y. J.; Sternlieb, B. J.; Cox, D. E.; Brewer, Jess H.; Kadono, R.; Kempton, J. R.; Kiefl, R. F.; Kreitzman, S. R.; Luke, G. M.; Mulhern, P. J.; Riseman, T. M.; Williams, Dudley; Kossler, W. J.; Yu, Xiao-Dong; Stronach, C. E.; Subramanian, M.A.; Gopalakrishnan, J.; Sleight, A.W.

doi:10.1038/335151a0

Cited by 87 publications

(39 citation statements)

References 8 publications

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“…Within the charge-spin separation fermion-spin theory 15 , the mechanism of superconductivity in the hole doped cuprates has been discussed 16 , where dressed holons interact occurring directly through the kinetic energy by exchanging the dressed spinon excitations, leading to a net attractive force between the dressed holons, then the electron Cooper pairs originating from the dressed holon pairing state are due to the charge-spin recombination, and their condensation reveals the SC ground-state. In this case, the electron SC transition temperature is determined by the dressed holon pair transition temperature, and is a nonmonotonic doping dependence, i.e., the SC transition temperature is maximal for a particular carrier concentration and decreases both for underdoped and overdoped regimes 16 , in agreement with experiments 9,10 . In this paper, we study the mechanism of superconductivity in the doped cobaltates along with this line.…”

supporting

confidence: 83%

“…Although the ferromagnetic correlation is present in Na x CoO 2 for the large electron doping concentration (x ≈ 0.7) 6 , the AF short-range spin correlation in Na x CoO 2 and Na x CoO 2 · yH 2 O in the low electron doping concentration (δ ≈ 0.35) has been observed from nuclear quadrupolar resonance and thermopower as well as other experimental measurements 1,4,5,7,8 . Moreover, the SC transition temperature displays the same kind of doping controlled behavior that is observed in the doped cuprates, i.e., the optimal SC transition temperature occurs in a narrow range of the electron doping concentration, and decreases for both underdoped and overdoped regimes 4,5 , in analogy to the phase diagram of the cuprate superconductors 9,10 . Therefore the superconductivity developed with the background of the AF spin correlation in the doped cobaltate suggests the importance of the strong electron correlation as in the doped cuprates [2][3][4]7 .…”

mentioning

confidence: 61%

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Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O

Liu

Liang

Feng

et al. 2005

Commun. Theor. Phys.

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Within the charge-spin separation fermion-spin theory, we have shown that the mechanism of superconductivity in the electron doped cobaltate NaxCoO2 · yH2O is ascribed to its kinetic energy. The dressed fermions interact occurring directly through the kinetic energy by exchanging magnetic excitations. This interaction leads to a net attractive force between dressed fermions, then the electron Cooper pairs originating from the dressed fermion pairing state are due to the charge-spin recombination, and their condensation reveals the superconducting ground state. The superconducting transition temperature is identical to the dressed fermion pair transition temperature, and is suppressed to a lower temperature due to the strong magnetic frustration. The optimal superconducting transition temperature occurs in the electron doping concentration δ ≈ 0.29, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the experimental results. The discovery of superconductivity in the doped cobaltate Na 0.35 CoO 2 · 1.3H 2 O has engendered great interest in transition metal oxides 1 . Although the superconducting (SC) transition temperature is much less than that in the doped cuprate superconductors, both systems share many common features. The doped cobaltate has a lamellar structure consisting of the two-dimensional (2D) CoO 2 layers separated by a thick insulating layer of Na + ions, where the one-half spin Co 4+ ions are arranged on a triangular lattice, and it becomes a superconductor after hydration that significantly enhances the distance between CoO 2 layers 1 . This structure is similar to the cuprate superconductors in the sense that they also have a layered structure of the square lattice of the CuO 2 plane separated by insulating layers 2 . The undoped cuprate is a Mott insulator with the antiferromagnetic (AF) longrange-order (AFLRO), then changing the carrier concentration by ionic substitution or increasing the oxygen content turns these compounds into the SC state leaving the AF short-range correlation still intact 2,3 . The optimal doping occurs at 0.15 holes (electrons) added to the half-filled band of the parent compound 2,3 . However, Na x CoO 2 · yH 2 O is viewed as an electron doped Mott insulator, where superconductivity appears with electron doping 1 . The optimal doping for superconductivity occurs at 0.3 electrons per Co above the ground-state Na 0.3 CoO 2 · 1.3H 2 O, which is a half-filled two-electron t 2g derived band 4,5 . Although the ferromagnetic correlation is present in Na x CoO 2 for the large electron doping concentration (x ≈ 0.7) 6 , the AF short-range spin correlation in Na x CoO 2 and Na x CoO 2 · yH 2 O in the low electron doping concentration (δ ≈ 0.35) has been observed from nuclear quadrupolar resonance and thermopower as well as other experimental measurements 1,4,5,7,8 . Moreover, the SC transition temperature displays the same kind of doping controlled behavior that is observed in the doped cuprates, i.e., the optimal SC transition temperature ...

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supporting

confidence: 83%

mentioning

confidence: 61%

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O

Liu

Liang

Feng

et al. 2005

Commun. Theor. Phys.

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“…(3) However, at all dopant concentrations these systems are diamagnetic [2,21,22,23,24], so their semiconducting phases are clearly not Mott insulators.…”

Section: I2 Summary Of Important Experimental Observationsmentioning

confidence: 99%

“…The diamagnetic contribution from the core, which constitutes almost the entire susceptibility in both the systems, when subtracted from the total susceptibility, leaves a tiny paramagnetic part which, in the lead-doped system, shows a somewhat unusual behaviour: it increases [2] as the system becomes more insulating, over the entire range of x ( Fig.I.7a). For the potassium-doped system the paramagnetic contribution remains nearly independent of x [2,6,7,21,22,23,24]. The paramagnetic contribution from the valence electrons is very small and lies between ≈ 0.8 to 2 ×10 −5 emu/mol in barium potassium bismuth oxide.…”

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confidence: 99%

The Exotic Barium Bismuthates

Taraphder

Pandit

Krishnamurthy

et al. 1996

Int. J. Mod. Phys. B

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We review the remarkable properties, including superconductivity, charge-densitywave ordering, and metal-insulator transitions, of lead-and potassium-doped barium bismuthate. We discuss some of the early theoretical studies of these systems. Our recent theoretical work, on the negative-U, extended-Hubbard model for these systems, is also described. Both the large-and intermediate-U regimes of this model are examined, using mean-field and random-phase approximations, particularly with a view to fitting various experimental properties of these bismuthates. On the basis of our studies, we point out possibilities for exotic physics in these systems. We also emphasize the different consequences of electronic and phonon-mediated mechanisms for the negative U. We show that, for an electronic mechanism, the semiconducting phases of these bismuthates must be unique, with their transport properties dominated by charge ±2e Cooperon bound states. This can explain the observed difference between the optical and transport gaps.We propose other experimental tests for this novel mechanism of charge transport and comment on the effects of disorder.PACS numbers: 74.10+v, 74.65+n * Present address: Mehta Research Institute of Mathematics and Mathematical Physics, 10 Kasturba Gandhi Marg, Allahabad-211002, India.† also at Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560012, India. 1The materials BaPb 1−x Bi x O 3 , and Ba 1−x K x BiO 3 , derived from barium bismuthate, BaBiO 3 , have many remarkable properties [1,2,3,4,5,6,7,8,9,10]. These include structural and metal-semiconductor transitions as x and the temperature T are varied; diamagnetic, semiconducting (CDW ordered?) phases even in the presence of a partially filled Bi 6s-O 2p σ antibonding band, with optical and transport gaps (2 eV and 0.24 eV, respectively, at x = 0) differing by nearly an order of magnitude; and superconducting T c 's (13K and 34K, respectively, for Pb and K doping) that are 3−5 times higher than for other three-dimensional oxide systems with similar, low densities of states at the Fermi level. However, partly because of all the attention devoted to the high-T c cuprates, these bismuthates have not been studied extensively, either experimentally or theoretically.We review here the experimental properties of lead-and potassium-doped barium bismuthate, give a summary of some early theoretical studies of these systems, and then provide an overview of our recent theoretical work [9,10], which uses the negative-U, extended-Hubbard model for these systems. The principal goal of our review is to consolidate what is known (experimentally and theoretically) about these remarkable materials.We have organised the review as follows: Section I is devoted to the phenomenology of lead-and potassium-doped barium bismuthate. Section II is devoted to a survey of the models that have been put forth for these systems and to some of the early theoretical work on them. Sections III and IV are devoted to our work on these systems based on the neg...

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“…The experimentally determined isotope effect coefficient a varied from 0.41±0.03 to 0.23±0.03 [Batiogg 1988, Hinks 1988, Kondoh 1989]. Although there is some square symbols are shown, zero resistance was not reached at any temperature above 10 K (after [Pei 1990] [Kondoh 1989, Uemura 1988. A CDW (Charge-Density-Wave) induced distortion is observed for the parent semiconductor, BaBiOs [Cox 1976[Cox ,1979, The K doping induces a insulator-metal phase transition.…”

Section: Superconductivity In Baixkxbi03mentioning

confidence: 99%

Photoemission study of some novel materials: rare earth/transition metal interface, Ba06K04BiO3 and AlPdMn

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Absence of magnetic order in (Ba, K)BiO3

Cited by 87 publications

References 8 publications

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O

The Exotic Barium Bismuthates

Photoemission study of some novel materials: rare earth/transition metal interface, Ba06K04BiO3 and AlPdMn

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Absence of magnetic order in (Ba, K)BiO3

Cited by 87 publications

References 8 publications

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na x CoO 2 · y H 2 O

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na x CoO 2 · y H 2 O

The Exotic Barium Bismuthates

Photoemission study of some novel materials: rare earth/transition metal interface, Ba06K04BiO3 and AlPdMn

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Product

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Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O

Kinetic Energy Driven Superconductivity in the Electron Doped Cobaltate Na _x CoO ₂ · y H ₂ O