Interplay of superconductivity and structural phase transition in the clathrate<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mn>6</mml:mn></mml:msub><mml:msub><mml:mi>Ge</mml:mi><mml:mn>25</mml:mn></mml:msub></mml:mrow></mml:math>

Yuan, H. Q.; Grosche, F. M.; Carrillo‐Cabrera, W.; Pacheco, V.; Sparn, G.; Baenitz, M.; Schwarz, Ulrich; Grin, Yu.; Steglich, F.

doi:10.1103/physrevb.70.174512

Cited by 23 publications

(12 citation statements)

References 18 publications

(28 reference statements)

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“…These estimated values in turn give almost the same V ¼ 2:3 eV regardless of a local Jahn-Teller distortion and strongly suggests that the change in T C observed between HP and AP can be explained mainly in terms of DOSðE F Þ. As previously implied by Grosche et al [6,10], the observed increase of T C can be interpreted in terms of the recovered higher DOSðE F Þ upon pressure in Ba 24 Ge 100 . When the same argument is applied to Ba 24 Si 100 with T C ¼ 1:4 K and Â D ¼ 515 K of Ba 24 Si 100 , we deduce ðBa 24 Si 100 Þ ¼ 0:47 and therefore V ¼ 2:6 eV using DOSðE F Þ ¼ 0:18 experimentally determined in the present work.…”

supporting

confidence: 76%

“…The framework of IV 100 has three types of nanospaces in the unit cell: eight pentagonal-dodecahedron centered on Ba (8c site), twelve open cages with larger accommodation space for Ba (12d site), and four pseudohexahedron for Ba (4a site). The structure contains both three-bonded and four-bonded IV atoms, in contrast to type-I clathrate consisting of only four-bonded framework atoms [10].…”

mentioning

confidence: 94%

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Electron-Phonon Interactions ofSi100andGe100Superconductors with Ba Atoms Inside

Tang

Heguri

et al. 2010

Phys. Rev. Lett.

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The absolute density of states of isostructural Ba24Si100 and Ba24Ge100 near the Fermi level, which is very relevant for discussion on phonon-mediated superconductivity, is quantitatively evaluated to be 0.28 states eV⁻¹/Ge atom and 0.18 states eV⁻¹/Si atom by combining soft x-ray photoelectron spectroscopy and magnetic susceptibility measurements. The energetics of the anharmonic motions of the endohedral Ba atoms are also discussed on the basis of the 4d-core-level spectra. The discussion based on these important physical parameters concludes that the unique electron-phonon interactions do not occur due to the local Jahn-Teller distortion of the fragile open cage structure in the phonon-mediated BCS formalism. Compounds with a rigid cage would be essential to give rise to anticipated unique interactions as a key ingredient favored for superconducting paring.

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supporting

confidence: 76%

mentioning

confidence: 94%

Electron-Phonon Interactions ofSi100andGe100Superconductors with Ba Atoms Inside

Tang

Heguri

et al. 2010

Phys. Rev. Lett.

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“…Ba 24 Ge 100 undergoes a two-step first-order phase transition between 230 and 180 K from metallic behavior to a high-resistivity state, 19,20 which is due to the Geu Ge bond breaking combined with the displacement of neighboring Ba atoms to the split positions. [21][22][23] However, BCS-like superconductivity occurs at low temperature T c = 0.24 K. By applying pressure, the phase transition is shifted to lower temperature, but T c increases remarkably to 3.8 K at 2.8 GPa. [19][20][21][22] These unusual properties are understood by the density of states at the Fermi energy.…”

Section: Introductionmentioning

confidence: 99%

“…[21][22][23] However, BCS-like superconductivity occurs at low temperature T c = 0.24 K. By applying pressure, the phase transition is shifted to lower temperature, but T c increases remarkably to 3.8 K at 2.8 GPa. [19][20][21][22] These unusual properties are understood by the density of states at the Fermi energy. 22,24 On the other hand, Ba 24 Si 100 showed a metallic conductivity without the phase transition down to 2 K at atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

High-pressure Raman study of the Ba-doped silicon clathrateBa24Si100up to27GPa

et al. 2005

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High-pressure Raman scattering of type-III silicon clathrate Ba 24 Si 100 has been measured up to 27 GPa at room temperature. Low-frequency vibrational modes associated with Ba atoms inside three kinds of cages were found around 45-90 cm −1 . The Si framework Raman bands were observed around 115-415 cm −1 , which are altogether shifted toward lower frequencies as compared to those of type-I Ba 8 Si 46 . High-pressure phase transition occurs at 6.5 GPa, which seems to be due to the structural distortion induced by the increasing guest͑Ba͒-host͑Si͒ couplings. Ba 24 Si 100 becomes irreversibly amorphous above 23 GPa. This pressure is lower than those of type-I Si clathrates, which suggests that type-III structure is less stable than type-I under high pressures.

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“…This material exhibits two structural changes under ambient conditions [81] involving shifts of both Ge and Ba atoms. The structural distortions induced under high-pressure conditions have been found to be associated with a large increase in g(E F ), which has been identified to be largely responsible for the enhanced T c [82].…”

Section: Superconductivity In Other Clathratesmentioning

confidence: 98%

Superconductivity and Magnetism in Silicon and Germanium Clathrates

Ross

2009

Nanoscale Magnetic Materials and Applications

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Clathrates are materials containing closed polyhedral cages stacked to form crystalline frameworks. With Si, Ge, and Sn atoms populating these frameworks, a wide variety of electronic and vibrational properties can be produced in these materials, by substitution upon framework sites or through incorporation of ions in cage-center positions. Commonly-formed structures include the type I, type II, and chiral clathrate types, whose properties will be described here. Ba 8 Si 46 with the type

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Interplay of superconductivity and structural phase transition in the clathrateBa6Ge25

Cited by 23 publications

References 18 publications

Electron-Phonon Interactions ofSi100andGe100Superconductors with Ba Atoms Inside

Electron-Phonon Interactions ofSi100andGe100Superconductors with Ba Atoms Inside

High-pressure Raman study of the Ba-doped silicon clathrateBa24Si100up to27GPa

Superconductivity and Magnetism in Silicon and Germanium Clathrates

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