Pressure-Induced Transition from a Correlated Insulator to a Fermi Liquid Observed in Geometrically Frustrated Hg_2Ru_2O_7 Pyrochlore(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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Recently discovered pyrochlore oxide, Hg_2Ru_2O_7, shows a first order metal-insulator transition at T〜107K. The effect of hydrostatic pressure on the M-I transition was studied by measuring the temperature dependent resistivity ρ(T) up to 12 GPa. The application of pressure suppressed the low temperature insulating state and eventually induced a transition from a correlated insulator to a metal at around 5 GPa. With decreasing temperature, ρ(T) in the metallic phase showed a rapid decrease at around T^*〜40K, likely representing the onset of a coherent-incoherent crossover, and eventually a well defined T^2-dependence at low temperatures, indicative of the presence of coherent quasi-particles. All these results point the formation of a Fermi liquid with an enhanced mass in the metallic state of this geometrically frustrated system, located close proximity to the correlation driven metal-insulator transition.
社団法人日本物理学会の論文
2007-06-15