Variation of the charge dynamics in bandwidth- and filling-controlled metal-insulator transitions of pyrochlore-type molybdates

I. Kézsmárki, N. Hanasaki, K. Watanabe, S. Iguchi, Y. Taguchi, S. Miyasaka, Y. Tokura

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The systematics of the bandwidth- and filling-controlled metal-insulator transitions (MITs) have been investigated for R2 Mo2 O7 family (R=Nd, Sm, Eu, Gd, Dy, and Ho) by infrared spectroscopy. The substantial role of electron correlation in driving the MIT is verified. With changing the R ionic radius (r) or equivalently the one-electron bandwidth (W), the MIT occurs in a continuous manner at rc ≈ r (R=Gd). The T=0 K gap continuously vanishes as Δ (rc -r), while at the metallic side the linear decrease of Drude weight is followed toward rc. In the metallic compounds, some of the infrared-active phonon modes show remarkably large Fano asymmetry correlating with the Drude weight. These Mo-O-Mo bending modes strongly couple to the conduction electrons via effective modulation of the bandwidth. Even for r rc a minimal level of hole doping closes the correlation gap, for example, the barely insulating Gd2 Mo2 O7 is turned to an incoherent metal by 5% partial substitution of Gd3+ with Ca2+. However, even on further doping no coherent electronic states are formed, indicating the role of the disorder-induced localization effect besides the dominant correlation effects.

Original languageEnglish
Article number125122
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume73
Issue number12
DOIs
Publication statusPublished - 2006

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Metal insulator transition
molybdates
insulators
bandwidth
Bandwidth
Doping (additives)
metals
Metallic compounds
Electron correlations
Electrons
Electronic states
Infrared spectroscopy
Substitution reactions
Metals
Modulation
conduction electrons
Infrared radiation
electrons
infrared spectroscopy
asymmetry

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Variation of the charge dynamics in bandwidth- and filling-controlled metal-insulator transitions of pyrochlore-type molybdates. / Kézsmárki, I.; Hanasaki, N.; Watanabe, K.; Iguchi, S.; Taguchi, Y.; Miyasaka, S.; Tokura, Y.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 73, No. 12, 125122, 2006.

Research output: Contribution to journalArticle

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