Crystal-field effects in the mixed-valence compounds Yb2M3Ga9 (M= Rh, Ir)

Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried out on single crystals of the intermediate valence compounds Yb2Rh3Ga9 and Yb2Ir3Ga9. These measurements reveal a large anisotropy due apparently to an interplay between crystalline electric field (CEF) and Kondo effects. The temperature dependence of magnetic susceptibility can be modelled using the Anderson impurity model including CEF within an approach based on the Non-Crossing Approximation.Comment: Accepted to Phys. Rev.

On the origin of heavy quasiparticles in LiV_2O_4

An explanation is provided for the heavy quasiparticle excitations in LiV_2O_4. It differs considerably from that of other known heavy-fermion systems. Main ingredients of our theory are the cubic spinel structure of the material and strong short-range correlations of the d electrons. The large gamma-coefficient is shown to result from excitations of Heisenberg spin 1/2 rings and chains. The required coupling constant is calculated from LDA+U calculations and is found to be of the right size. Also the calculated Sommerfeld-Wilson ratio is reasonably close to the observed one.Comment: REVTEX, 5 pages, 2 figure

Electronic Structure and Fermiology of PuCoGa5_5

By using a relativistic linear augmented-plane-wave method, we clarify energy band structures and Fermi surfaces of recently discovered plutonium-based superconductor PuCoGa$_5$. We find several cylindrical sheets of Fermi surfaces with large volume, very similar to CeMIn$_5$ (M=Ir and Co) isostructural with PuCoGa$_5$, in spite of different $f$-electron numbers between Ce$^{3+}$ and Pu$^{3+}$ ions. The similarity is understood by a concept of electron-hole conversion in a tight binding model constructed based on the $j$-$j$ coupling scheme. Based on the present results, we provide a possible scenario to explain why a transition temperature is so high as 18.5K in PuCoGa$_5$.Comment: 4 pages, Revtex, with 4 figures embedded in the text. Submitted to Phys. Rev. Let

Compressibility of CeMIn5Ce M In_5 and Ce2MIn8Ce_2 M In_8 (M = Rh, Ir and Co) Compounds

The lattice parameters of the tetragonal compounds Ce$M$In$_{5}$ and Ce$_{2}M$In$_{8}$($M=$Rh, Ir and Co) have been studied as a function of pressure up to 15 GPa using a diamond anvil cell under both hydrostatic and quasihydrostatic conditions at room temperature. The addition of $M$In$_{2}$ layers to the parent CeIn$_{3}$ compound is found to stiffen the lattice as the 2-layer systems (average of bulk modulus values $B_{0}$ is 70.4 GPa) have a larger $B_{0}$ than CeIn$_{3}$ (67 GPa), while the 1-layer systems with the are even stiffer (average of $B_{0}$ is 81.4 GPa). Estimating the hybridization using parameters from tight binding calculations shows that the dominant hybridization is $fp$ in nature between the Ce and In atoms. The values of $V_{pf}$ at the pressure where the superconducting transition temperature $T_{c}$ reaches a maximum is the same for all Ce$M$In$_{5}$ compounds. By plotting the maximum values of the superconducting transition temperature $T_{c}$ versus $c/a$ for the studied compounds and Pu-based superconductors, we find a universal $T_{c}$ versus $c/a$ behavior when these quantities are normalized appropriately. These results are consistent with magnetically mediated superconductivity.Comment: Updated version resubmitted to Phys. Rev.

An Experimental and Theoretical Study of the Variation of 4f Hybridization Across the La1-xCexIn3 Series

Crystal structures of a series of La1-xCexIn3 (x = 0.02, 0.2, 0.5, or 0.8) intermetallic compounds have been investigated by both neutron and X-ray diffraction, and their physical properties have been characterized by magnetic susceptibility and specific heat measurements. Our results emphasize atypical atomic displacement parameters (ADP) for the In and the rare-earth sites. Depending on the x value, the In ADP presents either an "ellipsoidal" elongation (La-rich compounds) or a "butterfly-like" distortion (Ce-rich compounds). These deformations have been understood by theoretical techniques based on the band theory and are the result of hybridization between conduction electrons and 4f-electrons.Comment: 7 pages, 8 figure

Magnetic structure of antiferromagnetic NdRhIn5

The magnetic structure of antiferromagnetic NdRhIn5 has been determined using neutron diffraction. It has a commensurate antiferromagnetic structure with a magnetic wave vector (1/2,0,1/2) below T_N = 11K. The staggered Nd moment at 1.6K is 2.6mu_B aligned along the c-axis. We find the magnetic structure to be closely related to that of its cubic parent compound NdIn3 below 4.6K. The enhanced T_N and the absence of additional transitions below T_N for NdRhIn5 are interpreted in terms of an improved matching of the crystalline-electric-field (CEF), magnetocrystalline, and exchange interaction anisotropies. In comparison, the role of these competing anisotropies on the magnetic properties of the structurally related compound CeRhIn5 is discussed.Comment: 4 pages, 4 figure

Superfluid to normal phase transition and extreme regularity of superdeformed bands

We derive the exact semiclassical expression for the second inertial parameter $\cal B$ for the superfluid and normal phases. Interpolation between these limiting values shows that the function ${\cal B}(I)$ changes sign at the spin $I_c$, which is critical for a rotational spectrum. The quantity $\cal B$ turns out to be a sensitive measure of the change in static pairing correlations. The superfluid-to-normal transition reveals itself in the specific variation of the ratio ${\cal B}/{\cal A}$ versus spin $I$ with the plateau characteristic of the normal phase. We find this dependence to be universal for normal deformed and superdeformed bands. The long plateau with a small value ${\cal B}/{\cal A}\sim A^{-8/3}$ explains the extreme regularity of superdeformed bands.Comment: 30 pages in LaTeX, 6 figures (PostScript). To be published in Yadernaya Fizika (Physics of Atomic Nuclei), special edition dedecated to the 90th birthday of Prof. I. I. Gurevit

Pharmacological levels of withaferin A (Withania somnifera) trigger clinically relevant anticancer effects specific to triple negative breast cancer cells

Withaferin A (WA) isolated from Withania somnifera (Ashwagandha) has recently become an attractive phytochemical under investigation in various preclinical studies for treatment of different cancer types. In the present study, a comparative pathway-based transcriptome analysis was applied in epithelial-like MCF-7 and triple negative mesenchymal MDA-MB-231 breast cancer cells exposed to different concentrations of WA which can be detected systemically in in vivo experiments. Whereas WA treatment demonstrated attenuation of multiple cancer hallmarks, the withanolide analogue Withanone (WN) did not exert any of the described effects at comparable concentrations. Pathway enrichment analysis revealed that WA targets specific cancer processes related to cell death, cell cycle and proliferation, which could be functionally validated by flow cytometry and real-time cell proliferation assays. WA also strongly decreased MDA-MB-231 invasion as determined by single-cell collagen invasion assay. This was further supported by decreased gene expression of extracellular matrix-degrading proteases (uPA, PLAT, ADAM8), cell adhesion molecules (integrins, laminins), pro-inflammatory mediators of the metastasis-promoting tumor microenvironment (TNFSF12, IL6, ANGPTL2, CSF1R) and concomitant increased expression of the validated breast cancer metastasis suppressor gene (BRMS1). In line with the transcriptional changes, nanomolar concentrations of WA significantly decreased protein levels and corresponding activity of uPA in MDA-MB-231 cell supernatant, further supporting its anti-metastatic properties. Finally, hierarchical clustering analysis of 84 chromatin writer-reader-eraser enzymes revealed that WA treatment of invasive mesenchymal MDA-MB-231 cells reprogrammed their transcription levels more similarly towards the pattern observed in non-invasive MCF-7 cells. In conclusion, taking into account that sub-cytotoxic concentrations of WA target multiple metastatic effectors in therapy-resistant triple negative breast cancer, WA-based therapeutic strategies targeting the uPA pathway hold promise for further (pre)clinical development to defeat aggressive metastatic breast cancer

Flaxino dark matter and stau decay

If the spontaneous breaking of Peccei-Quinn symmetry comes from soft supersymmetry breaking, the fermionic partners of the symmetry-breaking fields have mass of order the gravitino mass, and are called flatinos. The lightest flatino, called here the flaxino, is a CDM candidate if it is the lightest supersymmetric particle. We here explore flaxino dark matter assuming that the lightest ordinary supersymmetric particle is the stau, with gravity-mediated supersymmetry breaking. The decay of the stau to the flaxino is fast enough not to spoil the standard predictions of Big Bang Nucleosynthesis, and its track and decay can be seen in future colliders.Comment: 9 pages, 4 figures, to appear in JHE