316 research outputs found
Enhanced electron correlations in FeSb
FeSb has been recently identified as a new model system for studying
many-body renormalizations in a -electron based narrow gap semiconducting
system, strongly resembling FeSi. The electron-electron correlations in
FeSb manifest themselves in a wide variety of physical properties including
electrical and thermal transport, optical conductivity, magnetic
susceptibility, specific heat and so on. We review some of the properties that
form a set of experimental evidences revealing the crucial role of correlation
effects in FeSb. The metallic state derived from slight Te doping in
FeSb, which has large quasiparticle mass, will also be introduced.Comment: 9 pages, 7 figures; submitted to Annalen der Physi
Highly Dispersive Electron Relaxation and Colossal Thermoelectricity in the Correlated Semiconductor FeSb
We show that the colossal thermoelectric power, , observed in the
correlated semiconductor FeSb below 30\,K is accompanied by a huge Nernst
coefficient and magnetoresistance MR. Markedly, the latter two
quantities are enhanced in a strikingly similar manner. While in the same
temperature range, of the reference compound FeAs, which has a
seven-times larger energy gap, amounts to nearly half of that of FeSb, its
and MR are intrinsically different to FeSb: they are smaller
by two orders of magnitude and have no common features. With the charge
transport of FeAs successfully captured by the density functional theory,
we emphasize a significantly dispersive electron-relaxation time
due to electron-electron correlations to be at the heart of
the peculiar thermoelectricity and magnetoresistance of FeSb.Comment: 8 pages, 5 figure
Huge Thermoelectric Power Factor: FeSb2 versus FeAs2 and RuSb2
The thermoelectric power factor of the narrow-gap semiconductor FeSb2 is
greatly enhanced in comparison to the isostructural homologues FeAs2 and RuSb2.
Comparative studies of magnetic and thermodynamic properties provide evidence
that the narrow and correlated bands as well as the associated enhanced
thermoelectricity are only specific to FeSb2. Our results point to the
potential of FeSb2 for practical thermoelectric application at cryogenic
temperatures and stimulate the search for new correlated semiconductors along
the same lines.Comment: 14 pages, 4 figures, published in Applied Physics Expres
Intra- and Interband Electron Scattering in the Complex Hybrid Topological Insulator Bismuth Bilayer on BiSe
The band structure, intra- and interband scattering processes of the
electrons at the surface of a bismuth-bilayer on BiSe have been
experimentally investigated by low-temperature Fourier-transform scanning
tunneling spectroscopy. The observed complex quasiparticle interference
patterns are compared to a simulation based on the spin-dependent joint density
of states approach using the surface-localized spectral function calculated
from first principles as the only input. Thereby, the origin of the
quasiparticle interferences can be traced back to intraband scattering in the
bismuth bilayer valence band and BiSe conduction band, and to interband
scattering between the two-dimensional topological state and the
bismuth-bilayer valence band. The investigation reveals that the bilayer band
gap, which is predicted to host one-dimensional topological states at the edges
of the bilayer, is pushed several hundred milli-electronvolts above the Fermi
level. This result is rationalized by an electron transfer from the bilayer to
BiSe which also leads to a two-dimensional electron state in the
BiSe conduction band with a strong Rashba spin-splitting, coexisting
with the topological state and bilayer valence band.Comment: 11 pages, 5 figure
A Helium-Surface Interaction Potential of BiTe(111) from Ultrahigh-Resolution Spin-Echo Measurements
We have determined an atom-surface interaction potential for the
HeBiTe(111) system by analysing ultrahigh resolution measurements of
selective adsorption resonances. The experimental measurements were obtained
using He spin-echo spectrometry. Following an initial free-particle model
analysis, we use elastic close-coupling calculations to obtain a
three-dimensional potential. The three-dimensional potential is then further
refined based on the experimental data set, giving rise to an optimised
potential which fully reproduces the experimental data. Based on this analysis,
the HeBiTe(111) interaction potential can be described by a
corrugated Morse potential with a well depth , a
stiffness and a surface electronic
corrugation of % of the lattice constant. The improved
uncertainties of the atom-surface interaction potential should also enable the
use in inelastic close-coupled calculations in order to eventually study the
temperature dependence and the line width of selective adsorption resonances
Large Seebeck Effect by Charge-Mobility Engineering
The Seebeck effect describes the generation of an electric potential in a
conducting solid exposed to a temperature gradient. Besides fundamental
relevance in solid state physics, it serves as a key quantity to determine the
performance of functional thermoelectric materials. In most cases, it is
dominated by an energy-dependent electronic density of states at the Fermi
level, in line with the prevalent efforts toward superior thermoelectrics
through the engineering of electronic structure. Here, we demonstrate an
alternative source for the Seebeck effect based on charge-carrier relaxation: A
charge mobility that changes rapidly with temperature can result in a sizeable
addition to the Seebeck coefficient. This new Seebeck source is demonstrated
explicitly for Ni-doped CoSb3, where a dramatic mobility change occurs due to
the crossover between two different charge-relaxation regimes. Our findings
unveil the origin of pronounced features in the Seebeck coefficient of many
other elusive materials characterized by a significant mobility mismatch. As
the physical origin for the latter can vary greatly, our proposal provides a
unifying framework for the understanding of a large panoply of thermoelectric
phenomena. When utilized appropriately, this effect can also provide a novel
route to the design of improved thermoelectric materials for applications in
solid-state cooling or power generation.Comment: 12 pages, 4 figures and 1 tabl
trans-Dibromidobis(1-ethyl-3-methylimidazol-2-ylidene)palladium(II)
The title compound, trans-[PdBr2(C6H10N2)2], was synthesized ionothermally in the ionic liquid solvent 1-ethyl-3-methylimidazolium bromide. In the crystal, the PdII atoms are square-planarly coordinated to two Br atoms and two neutral (C6H10N2) ligands. The PdII atom is located on an inversion centre
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