Novel Features Realized in the Filled Skutterudite Structure

Sato, Hideyuki; Kikuchi, Daisuke; Tanaka, Kenya; Ueda, Makoto; Aoki, Hidekazu; Ikeno, Tsuyoshi; Tatsuoka, Sho; Kuwahara, K.; Aoki, Yuji; Kohgi, M.; Sugawara, Hitoshi; Iwasa, Kazuaki; Harima, Hisatomo

doi:10.1143/jpsjs.77sa.1

Cited by 29 publications

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“…T he ternary transition metal pnictides with the chemical formula MT 4 X 12 (M = alkali metal, alkaline earth, lanthanide, actinide; T = Fe, Ru, Os; X = P, As, Sb), which crystallize in the filled skutterudite structure (space group Im3), exhibit a wide variety of strongly correlated electron phenomena (1)(2)(3)(4). Many of these phenomena depend on hybridization between the rare earth or actinide f-electron states and the conduction electron states, which, in some filled skutterudite systems, leads to the emergence of semiconducting behavior.…”

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“…Although these systems have been studied in detail, the arsenide analogues have received considerably less attention, probably because of materials difficulties inherent to their synthesis. In this article, we present measurements of electrical resistivity ρ, magnetization M, specific heat C, and thermoelectric power S which show that CeOs 4 As 12 has a nonmagnetic or weakly magnetic semiconducting ground state with an energy gap in the range 45 K ≤ /k B ≤ 73 K and a small electronic specific heat coefficient γ ∼ 19 mJ/mol K 2 . Thus, we suggest that CeOs 4 As 12 may be a member of the class of compounds, commonly referred to as hybridization gap semiconductors or, in more modern terms, Kondo insulators.…”

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confidence: 99%

“…In this article, we present measurements of electrical resistivity ρ, magnetization M, specific heat C, and thermoelectric power S which show that CeOs 4 As 12 has a nonmagnetic or weakly magnetic semiconducting ground state with an energy gap in the range 45 K ≤ /k B ≤ 73 K and a small electronic specific heat coefficient γ ∼ 19 mJ/mol K 2 . Thus, we suggest that CeOs 4 As 12 may be a member of the class of compounds, commonly referred to as hybridization gap semiconductors or, in more modern terms, Kondo insulators. In these materials the localized f-electron states hybridize with the conduction electron states to produce a small gap (∼1-10 meV) in the electronic density of states.…”

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confidence: 99%

“…For a more complete discussion of the topic, we refer the reader to several excellent reviews (8,9). For comparison purposes, we also report results for the weakly magnetic analogue material LaOs 4 As 12 .…”

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The filled skutterudite CeOs ₄ As ₁₂ : A hybridization gap semiconductor

Baumbach

Sayles

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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X-ray diffraction, electrical resistivity, magnetization, specific heat, and thermoelectric power measurements are presented for single crystals of the new filled skutterudite compound CeOs 4 As 12 , which reveal phenomena that are associated with f-electron-conduction electron hybridization. Valence fluctuations or Kondo behavior dominates the physics down to T ∼ 135 K. The correlated electron behavior is manifested at low temperatures as a hybridization gapinsulating state. The small energy gap 1 /k B ∼ 73 K, taken from fits to electrical resistivity data, correlates with the evolution of a weakly magnetic or nonmagnetic ground state, which is evident in the magnetization data below a coherence temperature T coh ∼ 45 K. Additionally, the low-temperature electronic specific heat coefficient is small, γ ∼ 19 mJ/mol K 2 . Some results for the nonmagnetic analogue compound LaOs 4 As 12 are also presented for comparison purposes. Kondo insulator | rare earth compoundT he ternary transition metal pnictides with the chemical formula MT 4 X 12 (M = alkali metal, alkaline earth, lanthanide, actinide; T = Fe, Ru, Os; X = P, As, Sb), which crystallize in the filled skutterudite structure (space group Im3), exhibit a wide variety of strongly correlated electron phenomena (1-4). Many of these phenomena depend on hybridization between the rare earth or actinide f-electron states and the conduction electron states, which, in some filled skutterudite systems, leads to the emergence of semiconducting behavior. This trend is evident in the cerium transition metal phosphide and antimonide filled skutterudite systems, most of which are semiconductors where the gap size is correlated with the lattice constant (5-7). Although these systems have been studied in detail, the arsenide analogues have received considerably less attention, probably because of materials difficulties inherent to their synthesis. In this article, we present measurements of electrical resistivity ρ, magnetization M, specific heat C, and thermoelectric power S which show that CeOs 4 As 12 has a nonmagnetic or weakly magnetic semiconducting ground state with an energy gap in the range 45 K ≤ /k B ≤ 73 K and a small electronic specific heat coefficient γ ∼ 19 mJ/mol K 2 . Thus, we suggest that CeOs 4 As 12 may be a member of the class of compounds, commonly referred to as hybridization gap semiconductors or, in more modern terms, Kondo insulators. In these materials the localized f-electron states hybridize with the conduction electron states to produce a small gap (∼1-10 meV) in the electronic density of states. Depending on the electron concentration, the Fermi level can be found within the gap, yielding semiconducting behavior, or outside the gap, giving metallic heavy fermion behavior. For a more complete discussion of the topic, we refer the reader to several excellent reviews (8, 9). For comparison purposes, we also report results for the weakly magnetic analogue material LaOs 4 As 12 . Experimental DetailsSingle crystals of CeOs 4 As 12 and LaOs 4 As 12 w...

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confidence: 99%

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The filled skutterudite CeOs ₄ As ₁₂ : A hybridization gap semiconductor

Baumbach

Sayles

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The filled skutterudites are a well known class of compounds that have generated intense activity during the past three decades due to the wide variety of interesting electronic and magnetic phenomena that they exhibit and their promising thermoelectric properties [249][250][251]. Filled skutterudites have the chemical formula MT 4 X 12 where the "filler" atom M = La-Nd, Sm, Eu, Yb, U, Th, the transition metal T = Fe, Ru, Os, and the pnictogen X = P, As, Sb.…”

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Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

et al. 2010

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Standard models for simple metals and insulators often fail for systems based on elements with unstable d-or f -electron shells, where strong electronic correlations can generate new and unexpected states of matter. Such a scenario can often be induced when a magnetic phase transition is tuned to absolute zero temperature by an external control parameter such as chemical composition, pressure or magnetic field. At the resulting quantum critical point (QCP), emergent phenomena, such as unconventional superconductivity and novel magnetic phases are frequently observed. The temperature and energy dependences of the physical properties are also found to deviate from expectations for a simple Fermi liquid. This "non-Fermi-liquid" (NFL) behavior is commonly manifested as weak power laws and logarithmic divergences in the physical properties at low temperatures and is often found in a V-shaped region near a QCP, which has become the "classic" QCP phase diagram. However, there is also a growing number of materials where the NFL behavior either occurs far away from the QCP, within an ordered phase, or may not be associated with any putative QCP. Thus, after nearly 20 years of research, it remains unknown whether NFL physics is universal, or if a multitude of unique subclasses exist. In this article, we review research that has primarily been carried out in our laboratory on systems that exhibit NFL behavior that does not conform to the "classic" QCP scenario.

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