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We report the crystal structures and superconductivity (SC) of LaPt$_{x}$Si$_{2-x}$ ($0.5 \leq x \leq 1.0$) that are solid solutions of LaSi$_{2}$ and LaPtSi with centrosymmetric tetragonal ($I4_{1}/amd$, $D_{4h}^{19}$, \#141) and non-centrosymmetric tetragonal ($I4_{1}md$, $C_{4v}^{11}$, \#109) structures, respectively. It was found that at $0.86 \leq x \leq 1.00$, the non-centrosymmetric tetragonal symmetry is preserved, while partial disorder appears in alternating Pt and Si of the hyper-honeycomb network. The superconducting transition temperature $T_{\rm c}$ was drastically reduced from 3.9 K to 1.5 K as $x$ varies from 1.0 to 0.86. Additionally, a hexagonal phase with an AlB$_{2}$-type structure ($P6/mmm$, $D_{6h}^{1}$, \#191) has been discovered at $0.50 \leq x \leq 0.71$ with a honeycomb network of statistically distributed Pt and Si atoms. The hexagonal phase exhibited SC at $T_{\rm c} = 0.38$ K. This system provides an opportunity to investigate the relationship between topological electronic states, SC, and disorders

We have investigated the surface and bulk electronic structures of the superconducting type-II Dirac semimetal 1T-PdSeTe. The superconducting transition temperature $T_C = 3.2$ K was almost twice as high as $T_C = 1.6$ K in 1T-PdTe$_2$. Scanning transmission electron microscopy measurements showed homogeneously mixed Se and Te atoms in the chalcogen layers, consistent with the CdI$_2$-type crystal structure. Angle-resolved photoemission spectroscopy measurements and density functional theory calculations indicated the existence of the topological surface states, and the overall band structures were similar to those of 1T-PdTe$_2$. These results suggest that CdI$_2$-type lattice symmetry dictates the band dispersion, regardless of atomic disorder in the chalcogen layers. As the electronic band dispersion and the local structures were persistent upon substitution, the enhancement of $T_C$ is likely associated with the chemical pressure. Our results provide insight into the effects of the solid solution on the surface and bulk electronic states as well as the superconducting transition temperature., Comment: Quantum materials, Dirac semimetal, Weyl semimetal, Topological insulator, Topological superconductor, angle-resolved Photoemission spectroscopy, superconductivity

The anisotropic electronic structure and Drude response of the quasi-kagome Kondo lattice CeRhSn have been investigated by combining polarized optical conductivity measurements and first-principles band calculations. Along the hexagonal $a$- and $c$-axes, the peaks in the middle-infrared region originating from the hybridization between conduction bands and Ce $4f$ states appear even at room temperature, indicating strong valence fluctuation. Renormalized Drude responses observed at the photon energy below 100 meV, on the other hand, are characterized by non-Fermi-liquid-like scattering rate $1/\tau$ proportional to $\omega^1$ for $E \parallel a$ and $\omega^{1.5}$ for $E \parallel c$. Additionally, the heavy carrier response only for $E \parallel a$ obeyed the dynamical Planckian scaling below 80 K, suggesting that the quantum criticality only appears in the Ce quasi-kagone plane for $E \parallel a$. These results indicate that the quantum criticality with the strong valence fluctuation is realized in the Ce quasi-kagome lattice., Comment: 5 pages, 4 figures

We successfully synthesized a verdazyl-based complex, ($p$-Py-V-$p$-CN)$_2$[Cu(hfac)$_2$]. Molecular orbital calculations reveal that three types of antiferromagnetic (AF) interactions are involved in the formation of a spin-1/2 distorted octagonal lattice composed of the verdazyl radical and Cu spins. The magnetic properties of the compound exhibited contributions from AF correlations and a phase transition to an AF ordered state at approximately $T_{\rm{N}}$ = 2.5 K. Below $T_{\rm{N}}$, we observed a $T^2$ dependence of the specific heat, indicating dominant two-dimensional AF correlations within the octagonal lattice. The magnetization curve in the low-temperature region exhibited a low-field linear increase, subsequent bending at 1/3 magnetization, and high-field nonlinear increase. We reproduced the observed unique magnetic behavior through the numerical analysis based on the octagonal lattice. These results demonstrate that the present compound exhibits magnetic properties characteristic of octagonal lattice topology., Comment: 7 pages, 4 figures. arXiv admin note: text overlap with arXiv:2310.14569