Exotic Heavy-Fermion State in Filled Skutterudite SmOs₄Sb₁₂

Abstract

In this paper recent substantial progress in applying the density-matrix renormalizationgroup (DMRG) to the simulation of the time-evolution of strongly correlated quantum systems in one dimension is reviewed. Various approaches to generating a time-evolution numerically are considered. The key focus of this review is on current strategies to circumvent the limitations of the quite small subspace well approximated by DMRG, by either enlarging or changing it as time evolves. All these approaches can be extended to the simulation of mixed, i.e. finitetemperature states. While this paper is phrased almost entirely in standard DMRG language, I finish by considering the alternative formulation of time-evolutions in the language of matrix product states which is less well-known but conceptually more powerful.KEYWORDS: density-matrix renormalization-group, strongly correlated systems, quantum information theory IntroductionMore than ten years after the invention of the Density-Matrix Renormalization Group (DMRG) by Steve White, 1, 2 this method has become the method of choice for the numerical simulation of the equilibrium properties of strongly correlated one-dimensional quantum systems.3, 4 Ground-state properties of both bosonic and fermionic systems have been calculated often at almost machine precision and comparatively low computational cost. While these results have been of prime importance in understanding the details of gapped Haldane systems or critical Luttinger liquids, to name but a few applications, for a long time hardly any attention had been paid to the time-evolution of strongly correlated quantum systems, both due to the comparative lack of experimental input in the past and to the inherent difficulties of actually calculating such time-evolutions. The last years have seen an increasing number of experimental results on non-trivial time-evolutions. Perhaps most spectacular was the recent mastery of storing ultracold bosonic atoms in a magnetic trap superimposed by an optical lattice: This has allowed to drive these atoms, at will, by time-dependent variations of the optical lattice strength, from the superfluid (metallic) to the Mott insulating regime. These regimes are linked by one of the key phase transitions in strongly correlated systems.5 Quite generally, progress in the fields of nanoelectronics and spintronics raises the question how (strongly correlated) quantum many-body systems react to external timedependent perturbations and how transport can be calculated quantitatively also far from the linear-response regime. On the computational physicists' side, the last twelve months or so have seen an extraordinary surge of activity in developing DMRG variants applicable to timeevolutions, such that by now we have various very powerful and conceptually innovative DMRG algorithms for pure as well as mixed quantum states, for non-dissipative as well as dissipative dynamics.The relationship between these various algorithms is

Ultrasonic Study of the Ferromagnetic Heavy Fermion System SmFe4P12

“…In fact, the recent study indicates that SmOs 4 Sb 12 is most likely to be an itinerant ferromagnetic compound. 2) Next, the origin of the slight dip observed in (C 11 -C 12 )/2 around 60 K is discussed in terms of the quadrupole susceptibility of Sm ion. The elastic anomaly of a well-localized 4f electron system can usually be understood as the quadrupolar response of the system to external strain.…”

Fermi-surface topologies and low-temperature phases of the filled skutterudite compoundsCeOs4Sb12andNdOs4Sb12

“…These models have been used to explain the large magnetic-fieldindependent γ ≈ 820 mJmol −1 K −2 in SmOs 4 Sb 12 . 51,52 Previous ultrasonic measurements show an extra mode in NdOs 4 Sb 12 at T ≈ 15 K [53][54][55]; it and the abovementioned SmOs 4 Sb 12 are the only two skutterudites displaying this ultrasonic anomaly [53][54][55] . The contrast between the relatively low cyclotron effective masses in NdOs 4 Sb 12 and its relatively high γ value is therefore probably due to the local phonon modes.…”

Field-insensitive heavy fermion features and phase transition in the caged-structure quasi-skutterudite Sm3 Ru4 Ge13

“…The caged structure are also known for field-insensitive heavy fermion state [7,8] and mixed-valence [9,10]. For example, the filled-skutterudites of chemical formula RT 4 X 12 (R = rare earth, T = transition metal and X = P, As or Sb) display heavy fermion superconductivity, multipole ordering and unusual field-insensitive features in specific heat and in resistivity [11,12,7] which are also observed in the Frank-Kasper type caged structure intermetallics, RT 2 X 20 [13,14,15]. Both RT 4 X 12 and RT 2 X 20 display puzzling physics especially when R = Sm [16,17,18,5,7,19].…”

“…The field-insenstive phase transition in some of the Sm-based RT 2 X 20 has been attributed to octupolar ordering [16]. Though Sm-based heavy fermion systems are limited (e.g., SmPd 3 with γ = 280 mJ/mol K 2 and SmFe 4 P 12 with γ = 370 mJ/mol K 2 ), exotic heavy fermion state has been reported in the filled skutterudites SmOs 4 Sb 12 [7] and SmRu 4 P 12 [17]. The ternary intermetallic compounds denoted by the nominal stoichiometry R 3 T 4 X 13 [where R is either a rareearth element, an early d-block element such as Sc or Y, or an alkali-earth metal like Ca or Sr; T stands for a Group VIII d-electron element and X is In, Ge, or Sn] with R = Sm are less-explored systems in connection with heavy fermion physics or field-insensitive phase transitions.…”