Superconductivity in a pyrochlore oxide, Cd₂Re₂O₇

Abstract

We make the first report that a metallic pyrochlore oxide, Cd2Re2O7, exhibits type II superconductivity at 1.1 K. The pyrochlore oxide is known to be a geometrically frustrated system, which includes a tetrahedral network of magnetic ions. A large number of compounds are classified in the family of pyrochlore oxides, and these compounds exhibit a wide variety of physical properties ranging from insulator through semiconductor and from bad metal to good metal. Until now, however, no superconductivity has been reported for frustrated pyrochlore oxides. The bulk superconductivity of this compound is confirmed by measurements of the resistivity and the alternating-current magnetic susceptibility. The upper critical field Hc2, which is extrapolated to 0 K, is estimated as about 0.8 T, using the resistivity measurements under an applied field. The plot of Hc2 versus T indicates that the Cooper pairs are composed of rather heavy quasiparticles. This fact suggests that frustrated heavy electrons become superconducting in this compound.

Magnetic penetration depth inRbOs2O6studied by muon spin rotation

“…7 are scaled to the µSR value of λ(1.75 K) at µ 0 H =1 T. It is seen that between 0.6 T and 4.8 T the λ vs H dependence is almost flat. A linear fit of the data in this field range yields a slope η = −0.07 (2), in agreement with the η value obtained from the µSR experiment.…”

“…1,2,3,4,5,6,7,8 However, till now there is no agreement about the nature of superconducting pairing mechanism in these compounds. From the one hand, based on the results of the specific heat, 9 nuclear quadrupole resonance (NQR) 10 and muon-spin rotation (µSR) 11,12 experiments, Cd 2 Re 2 O 7 is suggested to be a weak-coupled isotropic BCS superconductor.…”

Goldstone-Mode Phonon Dynamics in the PyrochloreCd2Re2O7

“…In this Letter, we report polarized Raman investigations of the superconducting oxide Cd 2 Re 2 O 7 [6,7,8], which shows evidence of Goldstone phonon mode behavior. To the best of our knowledge, this is the first observation of a Goldstone optical phonon mode in a crystalline solid.…”

Low Temperature Symmetry of Pyrochlore Oxide Cd2Re2O7

“…1). Recently, Hanawa et al and the others reported the first superconductor Cd 2 Re 2 O 7 (T c =1 K) in the family of pyrochlore oxides [4,5,6]. The compound exhibits two more phase transitions at T s1 =200 K and T s2 =120 K, where electrical and magnetic properties change dramatically [7,8,9].…”