Superconductivity in the geometrically frustrated pyrochloreRbOs2O6

Abstract

We report the basic thermodynamic properties of the new geometrically frustrated β-pyrochlore bulk superconductor RbOs 2 O 6 with a critical temperature T c = 6.4 K. Specific heat measurements are performed in magnetic fields up to 12 T. The electronic density of states at the Fermi level in the normal state results in γ = (33.7 ± 0.2) mJ/mol f.u. /K 2 . In the superconducting state, the specific heat follows conventional BCS-type behavior down to 1 K, i.e. over three orders of magnitude in specific heat data. The upper critical field slope at T c is 1.2 T/K, corresponding to a Maki-parameter α = 0.64 ± 0.1. From the upper critical field µ 0 H c2 ≈ 6 T at 0 K, we estimate a Ginzburg-Landau coherence length ξ ≈ 74 Å. RbOs 2 O 6 is the second reported metallic AB 2 O 6 type pyrochlore compound after KOs 2 O 6 , and one of only three pyrochlore superconductors in addition to Cd 2 Re 2 O 7 and KOs 2 O 6 .

Large mass enhancement in

“…RbOs2O6 is one of only four pyrochlore superconductors known to date. These are the α-pyrochlore Cd2Re2O7 and the β-pyrochlores AOs2O6, where A = Cs, Rb, or K. [1,2,3] RbOs2O6 is a conventional s-wave superconductor with a critical temperature Tc = 6.4 K. [4,5,6,7] In this short paper, we provide evidence for an additional electronic mass enhancement beyond the contribution from the coupling to phonons. Specific heat measurements on RbOs2O6 show that the residual Sommerfeld coefficient in the superconducting state γr and the normal-state coefficient γ vary among the various samples measured.…”

Magnetic and charge transport properties of the Na-based Os oxide pyrochlore

“…To date, many studies seem to focus on the possibility; however correlations between the anomalous lattice properties and the superconductivity are still under debate [4][5][6][7][8][9][10][11][12][13]. Further additional studies are expected to help to make clear the issue.…”

Effect of electron-phonon coupling on the superconducting transition temperature in dodecaboride superconductors: A comparison ofLuB12withZrB12Teyssier1, Lortz2, Petrović3 et al. 2008Phys. Rev. B464410View full textAdd to dashboardCite

“…Such materials are particularly interesting when they become superconducting since they then represent model systems for studying electron-phonon interactions: The phonon mode responsible for superconductivity can be easily extracted from simple thermodynamic and transport experiments. 7,8 Apart from the borides, superconductors with similar structures are found, for example, among the pyrochlores 9,10 or the clathrates. [11][12][13][14] Strong covalent bonds between the boron atoms in B 12 cages lead to a very rigid lattice with a high Debye temperature.…”