STM imaging of a bound state along a step on the surface of the topological insulator Bi2_2Te3_3

Detailed study of the LDOS associated with the surface-state-band near a step-edge of the strong topological-insulator Bi2Te3, reveal a one-dimensional bound state that runs parallel to the stepedge and is bound to it at some characteristic distance. This bound state is clearly observed in the bulk gap region, while it becomes entangled with the oscillations of the warped surface band at high energy, and with the valence band states near the Dirac point. Using the full effective Hamiltonian proposed by Zhang et al., we obtain a closed formula for this bound state that fits the data and provide further insight into the general topological properties of the electronic structure of the surface band near strong structural defects.Comment: 5 pages, 4 figure

Generic dialogue modeling for multi-application dialogue systems

We present a novel approach to developing interfaces for multi-application dialogue systems. The targeted interfaces allow transparent switching between a large number of applications within one system. The approach, based on the Rapid Dialogue Prototyping Methodology (RDPM) and the Vector Space model techniques from Information Retrieval, is composed of three main steps: (1) producing finalized dia logue models for applications using the RDPM, (2) designing an application interaction hierarchy, and (3) navigating between the applications based on the user's application of interest

Evidence for nodal superconductivity in LaFePO

In several iron-arsenide superconductors there is strong evidence for a fully gapped superconducting state consistent with either a conventional s-wave symmetry or an unusual $s_\pm$ state where there the gap changes sign between the electron and hole Fermi surface sheets. Here we report measurements of the penetration depth $\lambda(T)$ in very clean samples of the related iron-phosphide superconductor, LaFePO, at temperatures down to $\sim$ 100 mK. We find that $\lambda(T)$ varies almost perfectly linearly with $T$ strongly suggesting the presence of gap nodes in this compound. Taken together with other data, this suggests the gap function may not be generic to all pnictide superconductors