1,841 research outputs found
Resonant States in the Electronic Structure of the High Performance Thermoelectrics AgPb_{2+m}$ ; The Role of Ag-Sb Microstructures
Ab initio electronic structure calculations based on gradient corrected
density functional theory were performed on a class of novel quaternary
compounds AgPb_{2+m}$, which were found to be excellent high
temperature thermoelctrics with large figure of merit ZT ~2.2 at 800K. We find
that resonant states appear near the top of the valence and bottom of the
conduction bands of bulk PbTe when Ag and Sb replace Pb. These states can be
understood in terms of modified Te-Ag(Sb) bonds. Electronic structure near the
gap depends sensitively on the microstructural arrangements of Ag-Sb atoms,
suggesting that large ZT values may originate from the nature of these ordering
arrangements.Comment: Accepted in Physical Review Letter
Single crystal growth and anisotropy of CeRuPO
We report on the single crystal growth of the ferromagnetic Kondo lattice
system CeRuPO using a Sn flux method. Magnetic susceptibility and electrical
resistivity measurements indicate strong anisotropy of this structurally
layered compound. They evidence that the magnetic moments order
ferromagnetically along the c-direction of the tetragonal unit cell, whereas
the crystal electric field (CEF) anisotropy favors the ab-plane. Therefore,
CeRuPO presents the unusual case within rare earth systems, where the
anisotropy of the interionic exchange interaction overcomes the single ion
anisotropy due to the CEF interaction.Comment: 13 pages, 7 figures, high quality figures:
http://www.cpfs.mpg.de/~krellner
New Candidates for Topological Insulators : Pb-based chalcogenide series
Here, we theoretically predict that the series of Pb-based layered
chalcogenides, PbBiSe and PbSbTe, are possible
new candidates for topological insulators. As increases, the phase
transition from a topological insulator to a band insulator is found to occur
between and 3 for both series. Significantly, among the new topological
insulators, we found a bulk band gap of 0.40eV in PbBiSe which is one
of the largest gap topological insulators, and that PbSbTe is
located in the immediate vicinity of the topological phase boundary, making its
topological phase easily tunable by changing external parameters such as
lattice constants. Due to the three-dimensional Dirac cone at the phase
boundary, massless Dirac fermions also may be easily accessible in
PbSbTe
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