Signatures of topology in ballistic bulk transport of HgTe quantum wells

We calculate bulk transport properties of two-dimensional topological insulators based on HgTe quantum wells in the ballistic regime. Interestingly, we find that the conductance and the shot noise are distinctively different for the so-called normal regime (the topologically trivial case) and the so-called inverted regime (the topologically non-trivial case). Thus, it is possible to verify the topological order of a two-dimensional topological insulator not only via observable edge properties but also via observable bulk properties. This is important because we show that under certain conditions the bulk contribution can dominate the edge contribution which makes it essential to fully understand the former for the interpretation of future experiments in clean samples.Comment: 5 pages, 4 figure

Use of statins and the risk of new onset Diabetes Mellitus

Indexación: Web of Science; ScieloSe ha descrito relación entre el uso de estatinas y aparición de nueva diabetes. Se revisa advertencia de la FDA, así como análisis de estudios y meta análisis, que permiten deducir una acción de las estatinas que favorece el desarrollo de nueva diabetes. Las precauciones del uso de estatinas se deben orientar a pacientes con factores de riesgo de diabetes en prevención primaria cardiovascular. Se expresa la necesidad de estudios prospectivos con objetivos primarios específicos, para mayor precisión de información y adopción de recomendaciones basadas en alto nivel de evidencias.Relationship between statin use and appearance of new diabetes has been described. We review the FDA warning and analysis of studies and meta-analysis, which point to an action of statins which favors the development of new diabetes. Precautions of statin use should guide patients with risk factors for diabetes in primary cardiovascular prevention. It expresses the need for prospective studies with specific primary objectives, for accuracy of information and making recommendations based on high-level evidence.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-85602012000300007&nrm=is

Single valley Dirac fermions in zero-gap HgTe quantum wells

Dirac fermions have been studied intensively in condensed matter physics in recent years. Many theoretical predictions critically depend on the number of valleys where the Dirac fermions are realized. In this work, we report the discovery of a two dimensional system with a single valley Dirac cone. We study the transport properties of HgTe quantum wells grown at the critical thickness separating between the topologically trivial and the quantum spin Hall phases. At high magnetic fields, the quantized Hall plateaus demonstrate the presence of a single valley Dirac point in this system. In addition, we clearly observe the linear dispersion of the zero mode spin levels. Also the conductivity at the Dirac point and its temperature dependence can be understood from single valley Dirac fermion physics.Comment: version 2: supplementary material adde

Surface state charge dynamics of a high-mobility three dimensional topological insulator

We present a magneto-optical study of the three-dimensional topological insulator, strained HgTe using a technique which capitalizes on advantages of time-domain spectroscopy to amplify the signal from the surface states. This measurement delivers valuable and precise information regarding the surface state dispersion within <1 meV of the Fermi level. The technique is highly suitable for the pursuit of the topological magnetoelectric effect and axion electrodynamics.Comment: Published version, online Sept 23, 201

Hamiltonian submanifolds of regular polytopes

We investigate polyhedral $2k$-manifolds as subcomplexes of the boundary complex of a regular polytope. We call such a subcomplex {\it $k$-Hamiltonian} if it contains the full $k$-skeleton of the polytope. Since the case of the cube is well known and since the case of a simplex was also previously studied (these are so-called {\it super-neighborly triangulations}) we focus on the case of the cross polytope and the sporadic regular 4-polytopes. By our results the existence of 1-Hamiltonian surfaces is now decided for all regular polytopes. Furthermore we investigate 2-Hamiltonian 4-manifolds in the $d$-dimensional cross polytope. These are the "regular cases" satisfying equality in Sparla's inequality. In particular, we present a new example with 16 vertices which is highly symmetric with an automorphism group of order 128. Topologically it is homeomorphic to a connected sum of 7 copies of $S^2 \times S^2$. By this example all regular cases of $n$ vertices with $n < 20$ or, equivalently, all cases of regular $d$-polytopes with $d\leq 9$ are now decided.Comment: 26 pages, 4 figure