Quasi-Two-Dimensional Fermi-Liquid State in Sr2RhO4-δ

概要

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Single crystals of layered perovskite Sr2RhO4-δ ($\delta=0.0$ and 0.1) are successfully grown by the floating-zone method. Stoichiometric single crystals (Sr2RhO4.0) are obtained by O2-annealing the as-grown crystals (Sr2RhO3.9). Sr2RhO4.0 and Sr2RhO3.9 show quasi-two-dimensional Fermi-liquid behavior at low temperatures, whereas there are large differences in the anisotropy of electrical resistivity $\rho_{c}$(3 K)/$\rho_{ab}$(3 K) and Wilson ratio $R_{\text{w}}$ between Sr2RhO4.0 and Sr2RhO3.9: $\rho_{c}$(3 K)/$\rho_{ab}$(3 K) = 2400 (19000) and $R_{\text{w}}=3.8$ (6.4) for Sr2RhO4.0 (Sr2RhO3.9). The differences observed between the temperature dependence of the in-plane electrical resistivity ($T<15$ K), magnetic susceptibility ($T<300$ K) and specific heat ($T<10$ K) of Sr2RhO4.0 and Sr2RhO3.9 are mainly derived from those between the density of states and band structure near the corresponding Fermi level. This indicates that the changes in these physical properties, which are accompanied by oxygen defects in the Sr2RhO4-δ system, can be explained by the rigid band model. Moreover, these results suggest that $t_{2g}$ band-filling can be controlled by adjusting the oxygen defect content $\delta$ in the Sr2RhO4-δ system. Although many similarities are observed in this study between the physical properties of Sr2RhO4.0 and Sr2RuO4, Sr2RhO4.0 does not exhibit superconductivity down to 36 mK.
2010-11-15