A topological insulator (TI) is an unusual quantum state in which the insulating bulk is topologically distinct from vacuum, resulting in a unique metallic surface that is robust against time-reversal invariant perturbations. The surface transport, however, remains difficult to isolate from the bulk conduction in most existing TI crystals (particularly Bi2Se3, Bi2Te3 and Sb2Te3) due to impurity caused bulk conduction. We report in large crystals of topological Kondo insulator (TKI) candidate material SmB6 the thickness-independent surface Hall effects and non-local transport, which persist after various surface perturbations. These results serve as proof that at low temperatures SmB6 has a metallic surface that surrounds an insulating bulk, paving the way for transport studies of the surface state in this proposed TKI material.

Strongly correlated Kondo insulator SmB 6 is known for its peculiar low temperature residual conduction, which has recently been demonstrated to arise from a robust metallic surface state, as predicted by the theory of topological Kondo insulator (TKI). Photoemission, quantum oscillation and magnetic doping experiments have provided evidence for the Dirac-like dispersion and topological protection. Questions arise as whether signatures of spin-momentum locking and electron interaction could be resolved in transport measurements. Here we report metallic conduction of surface state down to mK temperatures with saturation behaviors suggestive of Kondo effect. We observe in the surface state the weak-antilocalization (WAL) effect that is in agreement with a spin-momentum locked metallic surface. At larger perpendicular magnetic fields, the surface state exhibits an unusual linear magnetoresistance similar to those found in Bi-based topological insulators and in graphene.With its heavy f-electron degree of freedom, Kondo insulator (1) SmB 6 (2) behaves as a correlated metal at high temperatures. Below 40 K the bulk of SmB 6 becomes insulating with the opening of Kondo energy gap due to the hybridization between conduction electrons and the highly renormalized f-electrons. The theory (3) of topological Kondo insulator predicted the existence of a topologically protected surface state (TSS) within this Kondo gap, naturally explaining the mysterious resistance saturation below 4 K (1). Recent transport measurements (4-6) have confirmed the low temperature surface conduction and the robustness of the surface state (SS). This SS has been demonstrated (7) to vanish with a small amount of magnetic impurity but survives larger amount of non-magnetic doping, which is consistent with a TSS protected by time-reversal symmetry. Recent high resolution ARPES (8-10) and quantum oscillation (11) experiments have provided tentative evidence for the Dirac dispersion of the surface carriers, as expected in a TSS. Furthermore, unlike usual topological SS, first principle calculations (12, 13) have predicted three surface Dirac bands residing at Γ and X/Y points, which agrees with ARPES-measured surface electronic structure (8-10), although the anticipated spin-momentum locking (14, 15) awaits spin-resolved measurements. In this paper we perform transport studies of the SmB 6 SS down to 20 mK, searching for transport signatures of spinmomentum locking and electron interaction effects.Extending our previous work (6), we have verified the existence of SS in SmB 6 samples down to 20mK with non-local transport and thickness dependent Hall effect measurements. In particular, Fig. 1A demonstrates the non-local measurement from sample S11 with both (100) and (101)

The effects of uniaxial compressive stress on the normal state 17 O nuclear magnetic resonance properties of the unconventional superconductor Sr2RuO4 are reported. The paramagnetic shifts of both planar and apical oxygen sites show pronounced anomalies near the nominal a-axis strain εaa ≡ εv, that maximizes the superconducting transition temperature, Tc. The spin susceptibility weakly increases on lowering the temperature below T 10 K, consistent with an enhanced density of states associated with passing the Fermi energy through a van Hove singularity. Although such a Lifshitz transition occurs in the γ band, formed by the Ru dxy states hybridized with in-plane O pπ orbitals, the large Hund's coupling renormalizes the uniform spin susceptibilty, which, in turn, affects the hyperfine fields of all nuclei. We estimate this "Stoner" renormalization, S, by combining the data with first-principles calculations and conclude that this is an important part of the strain effect, with implications for superconductivity.

Thickness-driven electronic phase transitions are broadly observed in different types of functional perovskite heterostructures. However, uncertainty remains whether these effects are solely due to spatial confinement, broken symmetry, or rather to a change of structure with varying film thickness. Here, this study presents direct evidence for the relaxation of oxygen-2p and Mn-3d orbital (p-d) hybridization coupled to the layer-dependent octahedral tilts within a La2/3Sr1/3MnO3 film driven by interfacial octahedral coupling. An enhanced Curie temperature is achieved by reducing the octahedral tilting via interface structure engineering. Atomically resolved lattice, electronic, and magnetic structures together with X-ray absorption spectroscopy demonstrate the central role of thickness-dependent p-d hybridization in the widely observed dimensionality effects present in correlated oxide heterostructures

Clinical decision support is a powerful tool for improving healthcare quality and patient safety. However, developing a comprehensive package of decision support interventions is costly and difficult. If used well, Web 2.0 methods may make it easier and less costly to develop decision support. Web 2.0 is characterized by online communities, open sharing, interactivity and collaboration. Although most previous attempts at sharing clinical decision support content have worked outside of the Web 2.0 framework, several initiatives are beginning to use Web 2.0 to share and collaborate on decision support content. We present case studies of three efforts: the Clinfowiki, a world-accessible wiki for developing decision support content; Partners Healthcare eRooms, web-based tools for developing decision support within a single organization; and Epic Systems Corporation's Community Library, a repository for sharing decision support content for customers of a single clinical system vendor. We evaluate the potential of Web 2.0 technologies to enable collaborative development and sharing of clinical decision support systems through the lens of three case studies; analyzing technical, legal and organizational issues for developers, consumers and organizers of clinical decision support content in Web 2.0. We believe the case for Web 2.0 as a tool for collaborating on clinical decision support content appears strong, particularly for collaborative content development within an organization.