Evolution of4felectron states in the metal-insulator transition ofPrRu4P12

Abstract

Magnetic excitations of the filled skutterudite PrRu4P12 exhibiting a metal-insulator (M-I) transition at TM−I = 63 K were studied by inelastic neutron scattering experiment. The spectra at temperatures much lower than TM−I are described as well-defined crystal-field excitations. With approaching TM−I, the excitation peaks broaden and shift considerably together with the temperature variation of the carrier number and the atomic displacement in the transition. The 4f-electron state evolve from the well localized state in the insulator phase to the strongly hybridized itinerant state by p-f mixing near TM−I. The hybridization is responsible for the M-I transition of PrRu4P12.

Pressure suppression of unconventional charge-density-wave state in PrRu4P12studied by optical conductivity

“…6 However, the non-magnetic reference LaRu 4 P 12 did not show a similar transition, although a very similar FS was expected. 4,5 This fact, together with the neutron 7,8 and Raman 9 experiments, strongly suggested the importance of conduction (c)-f electron hybridization in the MI transition. With theoretical considerations, [10][11][12] it is currently believed that a novel charge density wave (CDW) formation is responsible for the MI transition.…”

“…Unlike the conventional CDW where the spatial modulation is provided by strong electron-lattice coupling, in the CDW of PrRu 4 P 12 the modulation is provided by the formation of two Pr sublattices, where the crystal field-split 4f level scheme in one sublattice is different from that in the other. [7][8][9] The microscopic nature of the c-f hybridized electronic structure deserves further studies.…”

NMR Study of Filled Skutterudite Pr0.9Ce0.1Ru4P12

“…On the other hand, the spectrum has a shoulder peak in the insulating state, and it becomes broad upon cooling. It is reported that the two Pr sublattices exists in the insulating state in PrRu 4 P 12 [3], thus it might cause the broadening of the spectrum in Pr 0.9 Ce 0.1 Ru 4 P 12 . Furthermore, below 10 K in the low temperature metallic state, the spectrum is drastically changed and the peak maximum in the spectrum splits into two.…”

“…Among the filled skutterudites, PrRu 4 P 12 is known to undergo an exotic metal-insulator (M-I) transition due to an unconventional chargedensity-wave formation at 63 K [2], which originates from an interplay between conduction and Pr 4f electrons. The neutron inelastic scattering experiments revealed distinct crystal electric field (CEF) ground states for the two Pr sublattices; one has a singlet and the other has a triplet ground state [3]. In spite of the magnetic ground state for the half of Pr sites, no indication of magnetic ordering has been observed down to 60 mK [3].…”

“…The neutron inelastic scattering experiments revealed distinct crystal electric field (CEF) ground states for the two Pr sublattices; one has a singlet and the other has a triplet ground state [3]. In spite of the magnetic ground state for the half of Pr sites, no indication of magnetic ordering has been observed down to 60 mK [3]. The M-I transition has been ascribed theoretically to an antiferro-hexadecapole order or scalar order of 4f electrons based on a strong c-f hybridization without breaking the local symmetry at the Pr site [4,5].…”