Universal scaling and quantum critical behavior of CeRhSb(1-x)Sn(x)

We propose a universal scaling rho*chi=const of the electrical resistivity rho with the inverse magnetic susceptibility chi^(-1) below the temperature of the quantum-coherence onset for the Ce 4f states in CeRhSb(1-x)Sn(x). In the regime, where the Kondo gap disappears (x~0.12), the system forms a non-Fermi liquid (NFL), which transforms into a Fermi liquid at higher temperature. The NFL behavior is attributed to the presence of a novel quantum critical point (QCP) at the Kondo insulator - correlated metal boundary. The divergent behavior of the resistivity, the susceptibility, and the specific heat has been determined when approaching QCP from the metallic side.Comment: Sent to Phys. Rev. Let

Magnetic properties of R(1) 1-x R(2)x Al2 alloys

The Curie temperature and magnetic moment in the paramagnetic state of R(1)1-xGdx(2)Αl2 samples (R = La, Lu, Y) as functions of the concentration x (x E [0, 1]) lave been measured in [1, 2] and more recently (R = Zr) in [3]. A linear dependence of the Curie temperature TC and of the magnetic moment M versus x has been found with ΤC changing from zero (x = 0) to TC-= 170K (x = 1) and M changing from zero (x = 0) to M = 7.94 μ (x = 1), in such a way that M(x)/x = 7.94 μβ (x E [0, 1])

Kondo insulating state in CeRhSb1-xSnx as a function of carrier number and its subsequent metallization

A quantum critical point represents an essential singularity in the phase diagram of the electron-correlated compounds. In the CeRhSb1¡xSnx system we have observed a quantum criticality at the boundary Kondo insulator-non-Fermi liquid state. In this series of compounds, CeRhSb has a Kondo insulating ground state, whereas CeRhSn exhibits a non-Landau Fermi liquid behavior. In view of different types of behavior of CeRhSb and CeRhSn, we review the results of the solution in CeRhSb1¡xSnx and discuss the effect of a quasi-continuous change of the number of conduction electrons on the gap formation in the Kondo-insulating regime, as well as on the critical behawior appearance near the quantum critical point

Stabilization of Kondo semiconductor state by Sb doping of CeNi1-delta Sn1+delta and the general criterion of its appearance

Semimetallic off-stoichiometric CeNi1¡±Sn1+±¡xSbx system with ± ¼ 0:06 is shown to transform into a Kondo semiconductor upon the substitution of few percent of Sb for Sn. The full-gap formation is associated with f-electron localization induced by the combined effect of the collective Kondo-singlet formation and the atomic disorder. Namely, the extra valence electrons introduced with the Sb doping (one per Sb atom) contribute additionally to the formation of the collective Kondo spin-singlet state at low temperatures, as seen by a substantial reduction of the magnetic susceptibility. The precise general definition of the Kondo semiconductor is provided and the difference with either the simple band or the Mott{Hubbard insulators is stressed

Band gap stability in Kondo insulators

We report on magnetic measurements and electronic structure investigations of CeNiSn and CeRhSb. Both belong to the group of Kondo insulators. The magnetic susceptibility shows the nonmagnetic ground state for these compounds and their alloys. The 3d X-ray photoemission spectroscopy spectra show evidence for the mixed valence state of Ce in CeRhSb alloys, as also seen for CeNiSn, whereas the spectra for the La substituted (Ce,La)NiSn compounds show only evidence for a pure Ce 3+ ground state. We suggest the presence of Kondo-hole states in (Ce,La)RhSb. The location of the pseudogap in CeRhSb varies with the number of free electron, the valence of Ce, and the f—d hybridization. We discuss the similar crystallographic properties and the closed electronic structures of ZrNiSn-type semi-Heusler alloys and CeNiSn-type Kondo insulators

Structural properties of REM2Sn2 (RE=La, Ce and M=Ni, Cu)

The lattice parameters a and c of CeM2 Sn2 show an anomalous temperature dependence compared to the analogous variations for LaM 2 Sn2 . The anomaly Δa of thermal expansion for CeCu2 Sn2 has a maximum around 90 K, whereas Δc has a maximum near 140 K, near to the maximum of the magnetic resistivity Δp

“DistorX” program for analysis of structural distortions affecting X-ray diffraction patterns

For the purposes of research on strongly correlated electronic systems (SCES), a computer program, DistorX (Distortion or X-ray diffraction patterns), was created. The program is an interactive Jupyter notebook for simulating the effects of structural distortions on X-ray diffraction patterns. The program is designed to be universal, in that it may be successfully applied to a variety of structures. In previous reports, a structural transition from a cubic phase of Yb3Rh4Sn13 – type to the superlattice variantwas been observed at 160 K for a series of skutterudite-related Ce3M4Sn13 compounds, where M = Co, Ru or Rh. In this work, we use a specialized build of DistorX to simulate the low-temperature X-ray diffraction patterns of a distorted unit cell. The method described here obtains simulated XRD patterns from the atomic positions and permits investigation of crystal structure without imposed symmetry operations. We further indicate the crystallographic plane in which the distortion occurs, and explain the possible origin of CDW in these materials

Mixed Valence of Ce and Its Consequences on the Magnetic State of Ce9Ru4Ga5: Electronic Structure Studies

We report on X-ray photoelectron spectroscopy (XPS) and ab initio electronic structure investigations of a novel intermetallic material Ce9Ru4Ga5. The compound crystallizes with a tetragonal unit cell (space group I4mm) that contains three inequivalent Ce atoms sites. The Ce 3d core level XPS spectra indicated an intermediate valence (IV) of selected Ce ions, in line with the previously reported thermodynamic and spectroscopic data. The ab initio calculations revealed that Ce1 ions located at 2a Wyckoff positions possess stable trivalent configuration, whereas Ce2 ions that occupy 8d site are intermediate valent. Moreover, for Ce3 ions, located at different 8d position, a fractional valence was found. The results are discussed in terms of on-site and intersite hybridization effects

Hybridization gap in some ternary f-electron and d-electron intermetallics

In this work we have discussed electronic structure, structural and magnetic properties of the CeMX-type compounds, where M is a transition metal and X is an sp element. The main goal of this presentation is to find the influence of metal M on the coherent gap formation at the Fermi level in the Ce-Kondo insulators. We also discuss a similar semiconductor-like resistance anomaly of Fe2TiSn and CeNiSn-type Kondo insulators

Enhancing superconductivity of the nonmagnetic quasiskutterudites by atomic disorder

We investigated the effect of enhancement of superconducting transition temperature Tc by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La3M4Sn13, Ca3Rh4Sn13, Y5Rh6Sn18, Lu5Rh6Sn18; M = Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale x in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with T? c > Tc (dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of T? c 2Tc (dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase T? c in respect to the bulk Tc one and proposed a model that explains the T? c > Tc behavior in the series of nonmagnetic skutterudite-related compounds