Optical Evidence of Itinerant-Localized Crossover of 4f4f Electrons in Cerium Compounds

Cerium (Ce)-based heavy-fermion materials have a characteristic double-peak structure (mid-IR peak) in the optical conductivity [$\sigma(\omega)$] spectra originating from the strong conduction ($c$)--$f$ electron hybridization. To clarify the behavior of the mid-IR peak at a low $c$-$f$ hybridization strength, we compared the $\sigma(\omega)$ spectra of the isostructural antiferromagnetic and heavy-fermion Ce compounds with the calculated unoccupied density of states and the spectra obtained from the impurity Anderson model. With decreasing $c$-$f$ hybridization intensity, the mid-IR peak shifts to the low-energy side owing to the renormalization of the unoccupied $4f$ state, but suddenly shifts to the high-energy side owing to the $f$-$f$ on-site Coulomb interaction at a slight localized side from the quantum critical point (QCP). This finding gives us information on the change in the electronic structure across QCP.Comment: 6 pages, 4 figures. To appear in JPSJ (Letters

腎細胞癌の膵転移の1例

A case of asynchronous bilateral renal cell carcinoma with pancreatic metastasis is described. Left nephrectomy and tumorectomy in the right kidney were performed. Solitary metastasis to the pancreas without symptoms was treated by distal pancreatectomy with tumor and splenectomy. Although bilateral renal cell carcinomas were histologically renal cell carcinoma (clear cell subtype, grade 2), the resected pancreatic tumor was renal cell carcinoma with sarcomatoid change. Therefore, the metastatic tumor had a more malignant potential than the primary tumor. The pancreatic metastasis was seen at 6 years 10 months and 2 years 6 months after left nephrectomy and enucleation of the right renal tumors, respectively. The patient is alive without disease and is being treated by alpha-interferon for 12 months after distal pancreatectomy. A careful long-term follow-up of the patient with renal cell carcinoma seems to be necessary

Coordination environment around the lithium cation in solid Li₂(EMIm)(N(SO₂CF₃)₂)₃ (EMIm=1-ethyl-3-methylimidazolium): Structural clue of ionic liquid electrolytes for lithium batteries

Crystal structure of Li₂(EMIm)(N(SO₂CF₃)₂)₃ (EMIm = 1-ethyl-3-methylimidazolium cation) has been determined by single-crystal X-ray diffraction as a structural clue of ionic liquid electrolytes for lithium batteries. Li₂(EMIm)(N(SO₂CF₃)₂)₃ crystallizes in the space group P2₁/c, a = 15.184(3)Å, b = 11.358(3)Å, c = 21.249(5)Å, β = 111.454(12)°, Z = 4, V = 3561.18(14)ų. Two of the three N(SO₂CF₃)₂ anions have cis-conformations and the third anion shows a trans-conformation. The asymmetric unit contains two crystallographically independent lithium ions and both of them are trigonal-bipyramidally coordinated by five oxygen atoms of N(SO₂CF₃)₂ anions, forming a two-dimensional network. EMIm cation occupies a space in the network, weakly interacting with the anions

Direct Detection of the Wino- and Higgsino-like Neutralino Dark Matters at One-Loop Level

The neutralino-nucleon (\tilde{\chi}^0-N) scattering is an important process for direct dark matter searches. In this paper we discuss one-loop contributions to the cross section in the wino-like and Higgsino-like LSP cases. The neutralino-nucleon scattering mediated by the Higgs \tilde{\chi}^0\tilde{\chi}^0 and Z\tilde{\chi}^0\tilde{\chi}^0 couplings at tree level is suppressed by the gaugino-Higgsino mixing at tree level when the neutralino is close to a weak eigenstate. The one-loop contribution to the cross section, generated by the gauge interaction, is not suppressed by any SUSY particle mass or mixing in the wino- and Higgsino-like LSP cases. It may significantly alter the total cross section when \sigma_{\tilde{\chi}^0 N}\sim 10^{-45} cm^2 or less.Comment: 26 pages, 9 figures. Version to be published in Physical Review

Superconductivity in undoped T' cuprates with Tc over 30 K

Undoped cuprates have long been considered to be antiferromagnetic insulators. In this article, however, we report that superconductivity is achieved in undoped T'-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd). Our discovery was performed by using metal-organic decomposition (MOD), an inexpensive and easy-to-implement thin-film process. The keys to prepare the superconducting films are firing with low partial-pressure of oxygen and reduction at low temperatures. The highest Tc of undoped T'-RE2CuO4 is over 30 K, substantially higher than "electron-doped" analogs. Remarkably, Gd2CuO4, even the derivatives of which have not shown superconductivity so far, gets superconducting with Tconset as high as ~ 20 K. The implication of our discovery is briefly discussed.Comment: 22 pages, 5 figures, submitted to Physical Review Letter