On the importance of the electron-phonon coupling function on the superconducting transition temperature in dodecaboride superconductors: A comparison of LuB12 with ZrB12

Abstract

We report a detailed study of specific heat, electrical resistivity and optical spectroscopy in the superconducting boride LuB12 (Tc = 0.4 K) and compare it to the higher Tc compound ZrB12 (Tc = 6 K). Both compounds have the same structure based on enclosed metallic Lu or Zr ions in oversized boron cages. The infrared reflectivity and ellipsometry in the visible range allow us to extract the optical conductivity from 6 meV to 4 eV in the normal state from 20 to 280 K. By extracting the superconducting properties, phonon density of states and electron-phonon coupling function from these measurements we discuss the important factors governing Tc and explain the difference between the two compounds. The phonon density of states seems to be insignificantly modified by substitution of Zr with Lu. However, the soft vibrations of the metal ions in boron cages, responsible for the relatively high Tc in ZrB12, have almost no contribution to the electron-phonon coupling in LuB12.

References in corpus (10)

• Kramers-Kronig constrained variational analysis of optical spectra
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• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
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• Specific heat, magnetic susceptibility, resistivity and thermal expansion of the superconductor ZrB12
• Superconductivity in Geometrically Frustrated Pyrochlore RbOs2O6
• Tunneling and Magnetic Characteristics of Superconducting ZrB${}_{12}$ Single Crystals
• Optical properties and electronic structure of ZrB${}_{12}$
• Anomalous electron-phonon coupling probed on the surface of ZrB${}_{12}$ superconductor

Cited by in corpus (9)

• 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
• Crystal structure and low-energy Einstein mode in ErV${}_2$Al${}_{20}$ intermetallic cage compound
• Soft phonon modes in the vicinity of the structural quantum critical point
• Hall effect and symmetry breaking in non-magnetic metal with dynamic charge stripes
• Checkerboard-type patterns of charge stripes in two-gap superconductor ZrB12
• Suppression of Superconductivity in Lu${}_x$Zr${}_{1-x}$B${}_{12}$ : Evidence of Static Magnetic Moments Induced by Non-Magnetic Impurities
• Inhomogeneous superconductivity in LuxZr1-xB12 dodecaborides with dynamic charge stripes
• Observation of a crossover from nodal to gapped superconductivity in Lu${}_x$Zr${}_{1-x}$B${}_{12}$