17 research outputs found
Steady state imaging of the thoracic vasculature using inversion recovery FLASH and SSFP with a blood pool contrast agent
Steady-state magnetic resonance angiography of the thoracic vasculature in congenital heart disease using a blood pool contrast agent: evaluation of two different techniques
Evaluation of semi quantitative perfusion parameter maps generated based on a fully automated non-rigid motion correction during a first pass myocardial perfusion (FPMP) MRI
Structural and electrical study of the topological insulator SnBi2Te4 at high pressures
We report high-pressure X-ray diffraction and electrical measurements of the topological insulator SnBi2Te4 at room temperature. The pressure dependence of the structural properties of the most stable phase of SnBi2Te4 at ambient conditions (trigonal phase) have been experimentally determined and compared with results of our ab initio calculations. Furthermore, a comparison of SnBi2Te4 with the parent compound Bi2Te3 shows that the central TeSnTe trilayer, which substitutes the Te layer at the center of the TeBiTeBiTe layers of Bi2Te3, plays a minor role in the compression of SnBi2Te4. Similar to Bi2Te3, our resistance measurements and electronic band structure simulations in SnBi2Te4 at high pressure suggest that this compound exhibits a pressure-induced electronic topological transition or Lifshitz transition between 3.5 and 5.0 GPa. (C) 2016 Published by Elsevier B.V.We thank Dr. Philipp Urban for preparing the sample. This work has been performed under financial support from Spanish MINECO under projects MAT2013-46649-C4-2-P, MAT2015-71070-REDC and CTQ2015-67755-C2-1-R and from Spanish Ministerio de Educacion, Cultura y Deporte as part of "Programa Campus de Excelencia Internacional/Programa de Valoracion y Recursos Conjuntos de I + D + i VLC/CAMPUS" through projects SP20140701 and SP20140871. One of the experiments were performed at MSPD-BL04 beamline at ALBA Synchrotron with the collaboration of ALBA staff. J.A.S. thanks "Juan de la Cierva" fellowship program for funding. A. A.-C. and J.S.-B. are also grateful to Spanish MINECO for the FPI (BES-2013-066112) and Ramon y Cajal (RyC-2010-06276) fellowships. We acknowledge Diamond Light Source for time on beamline I15 under Proposal EE9102.Vilaplana Cerda, RI.; Sans Tresserras, JÁ.; Manjón Herrera, FJ.; Andrada-Chacón, A.; Sánchez-Benitez, J.; Popescu, C.; Gomis, O.... (2016). Structural and electrical study of the topological insulator SnBi2Te4 at high pressures. Journal of Alloys and Compounds. 685:962-970. https://doi.org/10.1016/j.jallcom.2016.06.170S96297068
Semiconductor Spintronics
Spintronics refers commonly to phenomena in which the spin of electrons in a
solid state environment plays the determining role. In a more narrow sense
spintronics is an emerging research field of electronics: spintronics devices
are based on a spin control of electronics, or on an electrical and optical
control of spin or magnetism. This review presents selected themes of
semiconductor spintronics, introducing important concepts in spin transport,
spin injection, Silsbee-Johnson spin-charge coupling, and spindependent
tunneling, as well as spin relaxation and spin dynamics. The most fundamental
spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling.
Depending on the crystal symmetries of the material, as well as on the
structural properties of semiconductor based heterostructures, the spin-orbit
coupling takes on different functional forms, giving a nice playground of
effective spin-orbit Hamiltonians. The effective Hamiltonians for the most
relevant classes of materials and heterostructures are derived here from
realistic electronic band structure descriptions. Most semiconductor device
systems are still theoretical concepts, waiting for experimental
demonstrations. A review of selected proposed, and a few demonstrated devices
is presented, with detailed description of two important classes: magnetic
resonant tunnel structures and bipolar magnetic diodes and transistors. In most
cases the presentation is of tutorial style, introducing the essential
theoretical formalism at an accessible level, with case-study-like
illustrations of actual experimental results, as well as with brief reviews of
relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure