Pressure Dependence of Upper Critical Field in β-Pyrochlore Oxides

Iguchi, Daisuke; Isono, T.; Machida, Yo; Izawa, K.; Salce, B.; Flouquet, J.; Ogusu, Hiroki; Yamaura, Jun‐ichi; Hiroi, Zenji

doi:10.1143/jpsjs.80sa.sa040

Cited by 3 publications

(4 citation statements)

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“…They have received much attention due to their exotic properties, especially as 'rattling-good' materials [1]. For example, Ge/Si clathrates and the filled skutterudites RT 4 Sb 12 (R = La or Ce, T = Fe or Co) are promising candidates for thermoelectric applications [2][3][4], and the β-pyrochlore oxides AOs 2 O 6 (A = Cs, Rb, K) show a unique variation in superconducting character from weak coupling to strong coupling [1,[5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Zhang

Kuo

et al. 2015

Supercond. Sci. Technol.

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Low-temperature thermal conductivity measurements were performed on the single crystal of caged-type superconductors Y 5 Rh 6 Sn 18 and Lu 5 Rh 6 Sn 18 down to 80 mK. In zero magnetic field, no residual linear term T 0 k is found for either superconductor. At low field, the T 0 k of these two superconductors shows weak field dependence. These results exclude the nodal superconducting gap in Y 5 Rh 6 Sn 18 as revealed by recent specific heat measurements, and suggest that the caged-type superconductors R 5 Rh 6 Sn 18 (R = Y and Lu) may have a common nodeless superconducting gap.

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Section: Introductionmentioning

confidence: 99%

Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Zhang

Kuo

et al. 2015

Supercond. Sci. Technol.

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“…7,15,17,39) Since the large atomic excursion survives down to low temperatures, strong electron-rattler interactions are generated, which give rise to a large scattering causing the T 2 resistivity to appear. The observed increases in coefficient A and the effective mass 30) with pressure mean that the electron-rattler interactions are enhanced, which is the reason why T c increases with pressure in phase I. In fact, there is a clear tendency, in β-pyrochlore oxides, for T c and A to increase simultaneously as the anharmonicity increases from the Cs to K compounds.…”

Section: Discussionmentioning

confidence: 96%

“…This is consistent with the findings of a recent HP heat capacity measurement by Iguchi et al: both the effective mass and the degree of jump in heat capacity at T c increase monotonically with increasing pressure up to P s . 30) Therefore, the increase in T c is due to this increase. One may think that pressure squeezes the cage, so that the rattling intensity or the anharmonicity of the potential inside the cage tends to be weakened.…”

Section: Discussionmentioning

confidence: 97%

“…27) More recently, Isono and coworkers have carried out HP heat capacity measurements in a DAC filled with Ar on single crystals of KOs 2 O 6 , RbOs 2 O 6 , and CsOs 2 O 6 and observed abrupt drops in T c at 5.2, 5.8, and 10.5 GPa, respectively. [28][29][30][31] Interestingly, they show that these drops in T c take place at the same lattice volume of approximately 0.988 nm 3 under HP for all the compounds, in which similar structural transitions to those observed in KOs 2 O 6 may occur. 27) In this study, we carried out resistivity measurements on a high-quality single crystal of RbOs 2 O 6 under HPs of up to 6 GPa to investigate the effects of pressure on the superconductivity in more detail and the rattling in the β-pyrochlore oxides.…”

Section: Introductionmentioning

confidence: 89%

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Superconductivity and Rattling under High Pressure in the β-Pyrochlore Oxide RbOs₂O₆

et al. 2011

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Rattling-induced superconductivity in the β-pyrochlore oxide RbOs 2 O 6 is investigated under high pressures up to 6 GPa. Resistivity measurements in a high-quality single crystal show that the superconducting transition temperature T c increases gradually from 6.3 K at ambient pressure to 8.8 K at 3.5 GPa, surprisingly remains almost constant at 8.8 ± 0.1 K in a wide pressure range between 3.5 (P o ) and 4.8 GPa, and suddenly drops to 6.3 K at P s = 4.9 GPa, followed by a gradual decrease with further pressure increase. Two anomalies in the temperature dependence of the normal-state resistivity are observed at P o < P < P s and P > P s , revealing the presence of two high-pressure phases corresponding to the changes in T c . The rattling of the Rb ion inside a cage made of Os and O atoms may be slightly and seriously modified in these high-pressure phases that probably have cages of reduced symmetry, respectively, so that electron-rattler interactions that govern the superconducting and transport properties of β-RbOs 2 O 6 are significantly affected. KEYWORDS: pyrochlore oxide, RbOs 2 O 6 , resistivity, high pressure, superconductivity, rattling to form a three-dimensional skeleton. 10) A virtual size mismatch between the guest A ion and the cage made of the octahedra allows the guest ion to move almost freely with an unusually large atomic excursion in an anharmonic potential inside the cage. 11) Since the mismatch becomes large from Cs to K with decreasing ionic radius of the A ions, the intensity of rattling is enhanced accordingly towards KOs 2 O 6 . Evidence of rattling in β-pyrochlore oxides has been obtained from structural analyses showing large atomic displacement parameters 10,12) or from heat capacity and spectroscopic measurements that showed Einstein-like modes with low energies of 2-7 meV. 5,6,[13][14][15][16][17] The rattling apparently affects the electronic properties of β-pyrochlores. A high resistivity and its anomalous temperature dependence, shown by a concave-downward curvature in a wide temperature range, have been observed and ascribed to a strong scattering of electrons by rattling. 18) Moreover, the increase observed in the spin-lattice relaxation rate of A-nucleus NMR arises from a strong electron-lattice coupling of the same origin. 18,19) Because of this large electron-rattler interaction, β-pyrochore oxides undergo superconducting transitions at relatively high temperatures of T c = 9.6, 6.3, and 3.3 K for A = K, Rb, and Cs, respectively. Nagao et al. suggested that superconductivity is induced by the rattling itself, because the estimated average frequency of phonons mediating Cooper pairing coincides with the energy of rattling for each of the three compounds. 7) Hattori and Tsunetsugu have investigated the role of rattling in the mechanism of superconductivity in the framework of a strong coupling theory of superconductivity and successfully reproduced the observed T c s. 20)Unique chemical trends for various parameters are observed in the series of β-pyrochlore oxides: the rattl...

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Rattling Good Superconductor: β-Pyrochlore Oxides AOs₂O₆

2012

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Pressure Dependence of Upper Critical Field in β-Pyrochlore Oxides

Cited by 3 publications

References 16 publications

Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Superconductivity and Rattling under High Pressure in the β-Pyrochlore Oxide RbOs₂O₆

Rattling Good Superconductor: β-Pyrochlore Oxides AOs₂O₆

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Pressure Dependence of Upper Critical Field in β-Pyrochlore Oxides

Cited by 3 publications

References 16 publications

Nodeless superconducting gap in the caged-type superconductors Y5Rh6Sn18and Lu5Rh6Sn18

Nodeless superconducting gap in the caged-type superconductors Y5Rh6Sn18and Lu5Rh6Sn18

Superconductivity and Rattling under High Pressure in the β-Pyrochlore Oxide RbOs2O6

Rattling Good Superconductor: β-Pyrochlore Oxides AOs2O6

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Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Superconductivity and Rattling under High Pressure in the β-Pyrochlore Oxide RbOs₂O₆

Rattling Good Superconductor: β-Pyrochlore Oxides AOs₂O₆