Phonon density of states, anharmonicity, electron-phonon coupling and possible multigap superconductivity in the clathrate superconductors Ba8Si46 and Ba24Si100: Why is Tc different in these two compounds?

Abstract

We report a detailed study of specific heat, electrical resistivity and thermal expansion in combination with inelastic neutron and inelastic X-ray scattering to investigate the origin of superconductivity in the two silicon clathrate superconductors Ba8Si46 and Ba24Si100. Both compounds have a similar structure based on encaged barium atoms in oversized silicon cages. However, the transition temperatures are rather different: 8 K and 1.5 K respectively. By extracting the superconducting properties, phonon density of states, electron-phonon coupling function and phonon anharmonicity from these measurements we discuss the important factors governing Tc and explain the difference between the two compounds.

31 pages, 2 tables, 12 figures

References in corpus (11)

• Superconductivity in diamond
• Specific heat in the superconducting and normal state (2-300 K, 0-16 Teslas), and magnetic susceptibility of the 38-K superconductor MgB2: evidence for a multicomponent gap
• Phenomenological two-gap model for the specific heat of MgB_2
• Specific heat of single crystal MgB_2: a two-band superconductor with two different anisotropies
• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
• Superconductivity mediated by a soft phonon mode: specific heat, resistivity, thermal expansion and magnetization of YB6
• Specific heat of Nb_3Sn: The case for a second energy gap
• Specific heat, magnetic susceptibility, resistivity and thermal expansion of the superconductor ZrB12
• Superconductivity in Geometrically Frustrated Pyrochlore RbOs2O6
• Doping and temperature dependence of electron spectrum and quasiparticle dispersion in doped bilayer cuprates
• Band structure calculations for Ba${}_6$Ge${}_{25}$ and Ba${}_4$Na${}_2$Ge${}_{25}$ clathrates

Cited by in corpus (9)

• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Phonon Mode Spectroscopy, Electron-Phonon Coupling and the Metal-Insulator Transition in Quasi-One-Dimensional M2Mo6Se6
• Rattling enhanced superconductivity in MV${}_2$Al${}_{20}$ (M = Sc, Lu, Y) intermetallic cage compounds
• Evidence of multiband superconductivity in the $\beta$-phase Mo${}_{1-x}$Re${}_x$ alloys
• Formation of Vacancies in Si- and Ge-based Clathrates: Role of Electron Localization and Symmetry Breaking
• Crystal structure and low-energy Einstein mode in ErV${}_2$Al${}_{20}$ intermetallic cage compound
• Strong electron-phonon coupling and multiband effects in the superconducting $\beta$-phase Mo${}_{1-x}$Re${}_x$ alloys
• Soft phonon modes in the vicinity of the structural quantum critical point
• Transport and thermodynamic properties under anharmonic motion in type-I Ba8Ga16Sn30 clathrate