Spatially Resolved NMR Relaxation Rate in a Noncentrosymmetric Superconductor

We numerically study the spatially-resolved NMR around a single vortex in a noncentrosymmetric superconductor such as CePt3Si. The nuclear spin-lattice relaxation rate 1/T1 under the influence of the vortex core states is calculated for an s+p-wave Cooper pairing state. The result is compared with that for an s-wave pairing state.Comment: 2 pages; submitted to Proc. of SCES'0

Basic Properties of a Vortex in a Noncentrosymmetric Superconductor

We numerically study the vortex core structure in a noncentrosymmetric superconductor such as CePt3Si without mirror symmetry about the xy plane. A single vortex along the z axis and a mixed singlet-triplet Cooper pairing model are considered. The spatial profiles of the pair potential, local density of states, supercurrent density, and radially-textured magnetic moment density around the vortex are obtained in the clean limit on the basis of the quasiclassical theory of superconductivity.Comment: 6 pages; submitted to Proc. of VORTEX I

Magnetic Properties of a Superconductor with no Inversion Symmetry

We study the magnetic properties of a superconductor in a crystal without $z \to -z$ symmetry, in particular how the lack of this symmetry exhibits itself. We show that, though the penetration depth itself shows no such effect, for suitable orientation of magnetic field, there is a magnetic field discontinuity at the interface which shows this absence of symmetry. The magnetic field profile of a vortex in the $x-y$ plane is shown to be identical to that of an ordinary anisotropic superconductor except for a shift in the $-z$ direction by ${\tilde \kappa} \lambda_x$ (see errata). For a vortex along $z$, there is an induced magnetization along the radial direction.Comment: J. Low Temp. Physics, 140, 67 (2005); with Errat

Real-time monitoring of the silicidation process of tungsten filaments at high temperature used as catalysers for silane decomposition

The scope of this work is the systematic study of the silicidation process affecting tungsten filaments at high temperature (1900ºC) used for silane decomposition in the hot-wire chemical vapour deposition technique (HWCVD). The correlation between the electrical resistance evolution of the filaments, Rfil(t), and the different stages of the their silicidation process is exposed. Said stages correspond to: the rapid formation of two WSi2 fronts at the cold ends of the filaments and their further propagation towards the middle of the filaments; and, regarding the hot central portion of the filaments: a initial stage of silicon dissolution into the tungsten bulk, with a random duration for as-manufactured filaments, followed by the inhomogeneous nucleation of W5Si3 (which is later replaced by WSi2) and its further growth towards the filaments core. An electrical model is used to obtain real-time information about the current status of the filaments silicidation process by simply monitoring their Rfil(t) evolution during the HWCVD process. It is shown that implementing an annealing pre-treatment to the filaments leads to a clearly repetitive trend in the monitored Rfil(t) signatures. The influence of hydrogen dilution of silane on the filaments silicidation process is also discussed

Non-Centrosymmetric Heavy-Fermion Superconductors

In this chapter we discuss the physical properties of a particular family of non-centrosymmetric superconductors belonging to the class heavy-fermion compounds. This group includes the ferromagnet UIr and the antiferromagnets CeRhSi3, CeIrSi3, CeCoGe3, CeIrGe3 and CePt3Si, of which all but CePt3Si become superconducting only under pressure. Each of these superconductors has intriguing and interesting properties. We first analyze CePt3Si, then review CeRhSi3, CeIrSi3, CeCoGe3 and CeIrGe3, which are very similar to each other in their magnetic and electrical properties, and finally discuss UIr. For each material we discuss the crystal structure, magnetic order, occurrence of superconductivity, phase diagram, characteristic parameters, superconducting properties and pairing states. We present an overview of the similarities and differences between all these six compounds at the end.Comment: To appear in "Non-Centrosymmetric Superconductors: Introduction and Overview", Lecture Notes in Physics 847, edited by E. Bauer and M. Sigrist (Springer-Verlag, Berlin Heidelberg, 2012) Chap. 2, pp. 35-7

Topological Superfluid in one-dimensional Ultracold Atomic System with Spin-Orbit Coupling

We propose a one-dimensional Hamiltonian $H_{1D}$ which supports Majorana fermions when $d_{x^{2}-y^{2}}$-wave superfluid appears in the ultracold atomic system and obtain the phase-separation diagrams both for the time-reversal-invariant case and time-reversal-symmetry-breaking case. From the phase-separation diagrams, we find that the single Majorana fermions exist in the topological superfluid region, and we can reach this region by tuning the chemical potential $\mu$ and spin-orbit coupling $\alpha_{R}$. Importantly, the spin-orbit coupling has realized in ultracold atoms by the recent experimental achievement of synthetic gauge field, therefore, our one-dimensional ultra-cold atomic system described by $H_{1D}$ is a promising platform to find the mysterious Majorana fermions.Comment: 5 papers, 2 figure

A heterotrimeric G protein of the Gi family is required for cAMP-triggered trafficking of aquaporin 2 in kidney epithelial cells

Vasopressin is the key regulator of water homeostasis in vertebrates. Central to its antidiuretic action in mammals is the redistribution of the water channel aquaporin 2 (AQP2) from intracellular vesicles to the apical membrane of kidney epithelial cells, an event initiated by an increase in cAMP and activation of protein kinase A. The subsequent steps of the signaling cascade are not known. To identify proteins involved in the AQP2 shuttle we exploited a recently developed cell line (CD8) derived from the rabbit cortical collecting duct and stably transfected with rat AQP2 cDNA. Treatment of CD8 cells with pertussis toxin (PTX) inhibited both the vasopressin-induced increase in water permeability and the redistribution of AQP2 from an intracellular compartment to the apical membrane. ADP-ribosylation studies revealed the presence of at least two major PTX substrates. Correspondingly, two alpha subunits of PTX-sensitive G proteins, Galphai2 and Galphai3, were identified by Western blotting. Introduction of a synthetic peptide corresponding to the C terminus of the Gi3 alpha subunit into permeabilized CD8 cells efficiently inhibited the cAMP-induced AQP2 translocation; a peptide corresponding to the alpha subunits of Gi1/2 was much less potent. Thus a member of the Gi family, most likely Gi3, is involved in the cAMP-triggered targeting of AQP2-bearing vesicles to the apical membrane of kidney epithelial cells

Muon-spin rotation study of the ternary noncentrosymmetric superconductors Li2PdxPt3−xB

We investigated the superconducting state of the noncentrosymmetric superconductors Li2PdxPt3−xB with superconducting transition temperature T c=5.16(8) K (x=2.25), 3.56(8) K (x=1.5) and 2.60 K (x=0) by means of muon-spin rotation (μSR) and specific heat experiments. The μSR relaxation rate σ sc was found to be constant at low temperatures for all the compounds. Data taken at different magnetic fields show that the magnetic penetration depth λ is field-independent for Li2Pd2.25Pt0.75B and Li2Pt3B. The electronic contribution to the specific heat measured in Li2Pd1.5Pt1.5B and Li2Pt3B increases exponentially at the lowest temperatures. These features suggest that the whole family of Li2PdxPt3−xB comprises single-gap s-wave superconductors across the entire doping regime