Anisotropic Physical Properties of the Kondo Semimetal CeCu1.11_{1.11}As2_2

The recently proposed novel materials class called Weyl-Kondo semimetal (WKSM) is a time reversal invariant but inversion symmetry broken Kondo semimetal in which Weyl nodes are pushed to the Fermi level by the Kondo interaction. Here we explore whether CeCu$_{1+x}$As$_2$ may be a new WKSM candidate. We report on its single-crystal growth, structure determination and physical properties investigation. Previously published studies on polycrystalline samples suggest that it is indeed a Kondo semimetal, which is confirmed by our investigations on single crystals. X-ray diffraction reveals that CeCu$_{1+x}$As$_2$ crystallizes in a tetragonal centrosymmetric structure, although the inversion symmetry could still be broken locally due to partially occupied Cu sites. Chemical analysis results in an average occupation $x$ = 0.11(1). The electrical resistivity increases logarithmically with decreasing temperature, and saturates below 10 K. A Kondo temperature $T_{\mathrm{K}}$ $\approx$ 4 K is extracted from entropy, estimated from the specific heat measurements. From Hall effect experiments, a charge carrier density of $8.8 \times 10^{20}$ cm$^{-3}$ is extracted, a value characteristic of a semimetal. The magnetization shows pronounced anisotropy, with no evidence of magnetic ordering down to 0.4 K. We thus classify CeCu$_{1.11}$As$_2$ as a tetragonal Kondo semimetal with anisotropic magnetic properties, with a possibly broken inversion symmetry, thus fulfilling the necessary conditions for a WKSM state.Comment: 6 pages, 4 figures, Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019

Two-dimensional conical dispersion in ZrTe5{\mathrm{ZrTe}}_{5} evidenced by optical spectroscopy

Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone’s lack of protection by the lattice symmetry immediately sparked vast discussions about the size and topological or trivial nature of a possible gap opening. Here, we report on a combined optical and transport study of ZrTe5, which reveals an alternative view of electronic bands in this material. We conclude that the dispersion is approximately linear only in the a-c plane, while remaining relatively flat and parabolic in the third direction (along the b axis). Therefore, the electronic states in ZrTe5 cannot be described using the model of 3D Dirac massless electrons, even when staying at energies well above the band gap 2Δ ¼ 6 meV found in our experiments at low temperatures

空間反転対称性を持たないd電子系物質の超伝導

京都大学0048新制・課程博士博士(理学)甲第17335号理博第3832号新制||理||1553(附属図書館)30101京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 前野 悦輝, 教授 松田 祐司, 准教授 藤本 聡学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

Boron induced structure modifications in Pd-Cu-B system: new Ti2Ni-type derivative borides Pd3Cu3B and Pd5Cu5B2

The final publication is available via https://doi.org/10.1039/C5DT05058H.The formation of two distinct derivative structures of Ti2Ni-type, interstitial Pd3Cu3B and substitutive Pd5Cu5B2, has been elucidated in Pd-Cu-B alloys from analysis of X-ray single crystal and powder diffraction data and supported by SEM. The metal atom arrangement in the new boride Pd3Cu3B (space group , W3Fe3C-type structure, a=1.1136(3) nm) follows the pattern of atom distribution in the CdNi-type structure. Pd5Cu5B2 (space group , a=1.05273(5) nm) exhibits a non-centrosymmetric substitutive derivative of the Ti2Ni-type structure. The reduction of symmetry on passing from Ti2Ni-type structure to Pd5Cu5B2 corresponds to the loss of the axis delivered by an ordered occupation of the Ni position (32e) by dissimilar atoms, Cu and B. In both structures, the boron atom has only contact to Pd forming [BPd6] octahedra in Pd3Cu3B and [BPd6] trigonal prisms in Pd5Cu5B2. Neither a perceptible homogeneity range nor mutual solid solubility was observed for two compounds at 600 °C, while in as cast conditions Pd5Cu5B2 exhibits extended homogeneity range formed by a partial substitution of Cu atoms (in 24f) by Pd (Pd5+xCu5-xB2, 0≤x≤1). Electrical resistivity measurements performed on Pd3Cu3B as well as on Pd-poor and Pd-rich termini of Pd5+xCu5-xB2 annealed at 600 °C and in as cast conditions respectively demonstrated the absence of any phase transitions for this compounds in the temperature region from 0.3 K to 300 K.Austrian Science Funds (FWF

Divergent Catalytic Approach from Cyclic Oxime Esters to Nitrogen-Containing Heterocycles with Group 9 Metal Catalysts

We report the divergent catalytic transformation of alkene-tethered isoxazol-5­(4<i>H</i>)-ones by using rhodium and cobalt catalysts to afford 2<i>H</i>-pyrroles (with Rh catalyst) and azabicyclic cyclopropanes (with Co catalyst). The rhodium-catalyzed 2<i>H</i>-pyrrole formation involving hydrogen shift is supported by deuterium-labeling experiments. The control experiments in the cobalt-catalyzed reaction indicate that the bicyclic aziridines as the primary product undergo a skeletal rearrangement assisted by metal iodide salts

Successive spin reorientations and rare earth ordering in Nd 0.5 Dy 0.5 Fe O 3 : Experimental and ab initio investigations

International audienc

Giant spontaneous Hall effect in a nonmagnetic Weyl–Kondo semimetal

Nontrivial topology in condensed-matter systems enriches quantum states of matter to go beyond either the classification into metals and insulators in terms of conventional band theory or that of symmetry-broken phases by Landau’s order parameter framework. So far, focus has been on weakly interacting systems, and little is known about the limit of strong electron correlations. Heavy fermion systems are a highly versatile platform to explore this regime. Here we report the discovery of a giant spontaneous Hall effect in the Kondo semimetal Ce3Bi4Pd3 that is noncentrosymmetric but preserves time-reversal symmetry. We attribute this finding to Weyl nodes—singularities of the Berry curvature—that emerge in the immediate vicinity of the Fermi level due to the Kondo interaction. We stress that this phenomenon is distinct from the previously detected anomalous Hall effect in materials with broken time-reversal symmetry; instead, it manifests an extreme topological response that requires a beyond-perturbation-theory description of the previously proposed nonlinear Hall effect. The large magnitude of the effect in even tiny electric and zero magnetic fields as well as its robust bulk nature may aid the exploitation in topological quantum devices.ISSN:0027-8424ISSN:1091-649