Electronic structure properties and BCS superconductivity in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>β</mml:mi></mml:mrow></mml:math>-pyrochlore oxides:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">KOs</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>

Saniz, R.; Medvedeva, Julia E.; Ye, Lin Hui; Shishidou, Tatsuya; Freeman, Arthur J

doi:10.1103/physrevb.70.100505

Cited by 42 publications

(42 citation statements)

References 28 publications

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“…The evolution of the bandstructure for the β pyrochlores from Cs to K is unexpectedly subtle, as reported in previous study [12,15,16]. Because almost no contributions to the bandstructure arise from alkali metals in β, the bandstructure is roughly scaled to the lattice constant: the smaller the lattice, where larger hybridizations occur, the smaller the calculated DOS, as shown in Fig.…”

Section: Bandstructure Calculationsmentioning

confidence: 70%

Chemical trends of superconducting properties in pyrochlore oxides

Hiroi

Yamaura

Yonezawa

et al. 2007

Physica C: Superconductivity and its Applications

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Chemical trends of fundamental superconducting parameters and normal-state properties are described for a family of pyrochlore oxide superconductors. Particularly, the change of T c from 1.0 K for α-pyrochlore Cd 2 Re 2 O 7 to 3.3 K (A = Cs), 6.3 K (Rb), and 9.6 K (K) for β-pyrochlore AOs 2 O 6 is discussed on the basis of the conventional BCS scheme. Enhanced T c and anomalous features observed for KOs 2 O 6 are ascribed to low-energy phonons probably coming from the rattling of the K cations.

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Section: Bandstructure Calculationsmentioning

confidence: 70%

Chemical trends of superconducting properties in pyrochlore oxides

Hiroi

Yamaura

Yonezawa

et al. 2007

Physica C: Superconductivity and its Applications

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“…21,42,72,73) The band structure near the Fermi level is given by a manifold of 12 bands arising from Os 5d and O 2p states with a total bandwidth of $3 eV. The formal valence of the metals is A þ or Os 5:5þ .…”

Section: Basic Electronic Structures Of the -Pyrochlore Oxidesmentioning

confidence: 99%

Rattling-Induced Superconductiviy in the β-Pyrochlore Oxides AOs₂O₆

et al. 2009

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The superconducting properties of two -pyrochlore oxides, CsOs 2 O 6 and RbOs 2 O 6 , are studied by thermodynamic and transport measurements using high-quality single crystals. It is shown that the character of superconductivity changes systematically from weak coupling for CsOs 2 O 6 to moderately strong coupling for RbOs 2 O 6 , and finally to extremely strong coupling with BCS-type superconductivity for KOs 2 O 6 , with increasing T c . Strong-coupling correction analyses of the superconducting properties reveal that a low-energy rattling mode of the alkali metal ions is responsible for the mechanism of the superconductivity in each compound. The large enhancement of T c from Cs to K is attributed to the increase in the electron-rattler coupling with decreasing characteristic energy of the rattling and with increasing anharmonicity. The existence of weak anisotropy in the superconducting gap or in the electron-rattler interactions is found for the Cs and Rb compounds.

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“…Although band structure calculations show that the K ion does not influence the density of states (DOS) at the Fermi level [7,8], it seems to affect several key properties [9]. In particular, the first order phase transition revealed by specific heat measurements in magnetic fields at the temperature T p ≈ 7.5 K has been ascribed to a "freezing" of its rattling motion [10].…”

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Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of theβ-PyrochloreKOs2O6

et al. 2008

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We performed the first scanning tunneling spectroscopy measurements on the pyrochlore superconductor KOs2O6 (Tc = 9.6 K) in both zero magnetic field and the vortex state at several temperatures above 1.95 K. This material presents atomically flat surfaces, yielding spatially homogeneous spectra which reveal fully-gapped superconductivity with a gap anisotropy of 30%. Measurements performed at fields of 2 and 6 T display a hexagonal Abrikosov flux line lattice. From the shape of the vortex cores, we extract a coherence length of 31-40Å, in agreement with the value derived from the upper critical field Hc2. We observe a reduction in size of the vortex cores (and hence the coherence length) with increasing field which is consistent with the unexpectedly high and unsaturated upper critical field reported.PACS numbers: 74.70. Dd, 74.50.+r, 74.25.Qt The discovery of superconductivity in the β-pyrochlore osmate compounds AOs 2 O 6 (A = K, Rb, Cs) [1] has highlighted the question of the origin of superconductivity in classes of materials which possess geometrical frustration [2,3]. Interest has been predominantly focused on the highest-T c compound KOs 2 O 6 which presents many striking characteristics. In particular, the absence of inversion symmetry in its crystal structure [4] raises the question of its Cooper pair symmetry and the possibility of spin singlet-triplet mixing [5,6].The pyrochlore osmate compound KOs 2 O 6 displays a critical temperature T c = 9.6 K, the largest in its class of materials (CsOs 2 O 6 and RbOs 2 O 6 which differ only by the nature of the alkali ion have T c s of 3.3 and 6.3 K respectively). Although band structure calculations show that the K ion does not influence the density of states (DOS) at the Fermi level [7,8], it seems to affect several key properties [9]. In particular, the first order phase transition revealed by specific heat measurements in magnetic fields at the temperature T p ≈ 7.5 K has been ascribed to a "freezing" of its rattling motion [10]. The negative curvature of the resistivity as a function of temperature also indicates a large electron-phonon scattering [11]. Specific heat measurements [12] suggest the coexistence of strong electron correlations and strong electron-phonon coupling, two generally antagonistic phenomena with respect to the superconducting pairing symmetry. The nature of the symmetry remains a controversial subject in the literature. NMR [13] and µSR [14] data suggest anisotropic gap functions with nodes whereas thermal conductivity experiments [15] favor a fully-gapped state.The peculiar behavior of KOs 2 O 6 is demonstrated by its upper critical magnetic field H c2 , whose temperature dependence is linear down to sub-Kelvin temperatures and whose amplitude is above the Clogston limit [16]. One possible interpretation is the occurrence of spin-triplet superconductivity driven by spinorbit coupling [5,6]. Alternatively, it has also been suggested that this behavior can be explained by the peculiar topology of the Fermi surface (FS) sheets of KOs ...

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Electronic structure properties and BCS superconductivity inβ-pyrochlore oxides:KOs2O6

Cited by 42 publications

References 28 publications

Chemical trends of superconducting properties in pyrochlore oxides

Chemical trends of superconducting properties in pyrochlore oxides

Rattling-Induced Superconductiviy in the β-Pyrochlore Oxides AOs₂O₆

Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of theβ-PyrochloreKOs2O6

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Electronic structure properties and BCS superconductivity inβ-pyrochlore oxides:KOs2O6

Cited by 42 publications

References 28 publications

Chemical trends of superconducting properties in pyrochlore oxides

Chemical trends of superconducting properties in pyrochlore oxides

Rattling-Induced Superconductiviy in the β-Pyrochlore Oxides AOs2O6

Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of theβ-PyrochloreKOs2O6

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Rattling-Induced Superconductiviy in the β-Pyrochlore Oxides AOs₂O₆