2,421 research outputs found
Giant Carrier Mobility in Single Crystals of FeSb2
We report the giant carrier mobility in single crystals of FeSb2. Nonlinear
field dependence of Hall resistivity is well described with the two-carrier
model. Maximum mobility values in high mobility band reach ~10^5 cm^2/Vs at 8
K, and are ~10^2 cm^2/Vs at the room temperature. Our results point to a class
of materials with promising potential for applications in solid state
electronics.Comment: 5 pages, 3 figures. Applied Physics Letters (in press
Optical investigation of the metal-insulator transition in
We present a comprehensive optical study of the narrow gap
semiconductor. From the optical reflectivity, measured from the far infrared up
to the ultraviolet spectral range, we extract the complete absorption spectrum,
represented by the real part of the complex optical
conductivity. With decreasing temperature below 80 K, we find a progressive
depletion of below cm, the
semiconducting optical gap. The suppressed (Drude) spectral weight within the
gap is transferred at energies and also partially piles up over a
continuum of excitations extending in the spectral range between zero and
. Moreover, the interaction of one phonon mode with this continuum leads
to an asymmetric phonon shape. Even though several analogies between
and were claimed and a Kondo-insulator scenario was also invoked for
both systems, our data on differ in several aspects from those of
. The relevance of our findings with respect to the Kondo insulator
description will be addressed.Comment: 17 pages, 5 figure
Dimer-dimer stacking interactions are important for nucleic acid binding by the archaeal chromatin protein Alba
Archaea use a variety of small basic proteins to package their DNA. One of the most widespread and highly conserved is the Alba (Sso10b) protein. Alba interacts with both DNA and RNA in vitro, and we show in the present study that it binds more tightly to dsDNA (double-stranded DNA) than to either ssDNA (single-stranded DNA) or RNA. The Alba protein is dimeric in solution, and forms distinct ordered complexes with DNA that have been visualized by electron microscopy studies; these studies suggest that, on binding dsDNA, the protein forms extended helical protein fibres. An end-to-end association of consecutive Alba dimers is suggested by the presence of a dimer-dimer interface in crystal structures of Alba from several species, and by the strong conservation of the interface residues, centred on Are and Phe(60). In the present study we map perturbation of the polypeptide backbone of Alba upon binding to DNA and RNA by NMR, and demonstrate the central role of Phe(60) in forming the dimer dimer interface. Site-directed spin labelling and pulsed ESR are used to confirm that an end-to-end, dimer dimer interaction forms in the presence of dsDNA.Publisher PDFPeer reviewe
Comparison of stray-light and diffraction-caused crosstalk in free-space optical interconnects
In this paper we investigate for the first time the effect of the crosstalk introduced due to laser beam imaging in a free-space optical interconnect (FSOI) system. Due to the overfill of the transmitter microlens array by the vertical cavity surface emitting laser (VCSEL) beam, one part of the signal is imaged by the adjacent microlens to another channel, possibly far from the intended one. Even though this causes increase in interchannel and intersymbol interference, to our knowledge this issue has been neglected so far. The numerical simulation has been performed using a combination of exact ray tracing and the beam propagation methods. The results show that some characteristics of stray-light crosstalk are similar to that of diffraction-caused crosstalk, where it is strongly dependent on the fill factor of the microlens, array pitch, and the channel density of the system. Despite the similarities, the stray-light crosstalk does not affect by an increase in the interconnection distance. As simulation models for optical crosstalk are numerically intensive, we propose here a crosstalk behavioural model as a useful tool for optimisation and design of FSOIs. We show that this simple model compares favourably with the numerical simulation models
Anisotropy in the magnetic and electrical transport properties of Fe1-xCrxSb2
We have investigated anisotropy in magnetic and electrical transport
properties of Fe1-xCrxSb2 (0<= x <=1) single crystals. The magnetic ground
state of the system evolves from paramagnetic to antiferromagnetic with gradual
substitution of Fe with Cr. Anisotropy in electrical transport diminishes with
increased Cr substitution and fades away by x=0.5. We find that the variable
range hopping (VRH) conduction mechanism dominates at low temperatures for
0.4<= x <=0.75.Comment: 5 pages, 6 figure
Direct Evidence for a Magnetic f-electron Mediated Cooper Pairing Mechanism of Heavy Fermion Superconductivity in CeCoIn5
To identify the microscopic mechanism of heavy-fermion Cooper pairing is an
unresolved challenge in quantum matter studies; it may also relate closely to
finding the pairing mechanism of high temperature superconductivity.
Magnetically mediated Cooper pairing has long been the conjectured basis of
heavy-fermion superconductivity but no direct verification of this hypothesis
was achievable. Here, we use a novel approach based on precision measurements
of the heavy-fermion band structure using quasiparticle interference (QPI)
imaging, to reveal quantitatively the momentum-space (k-space) structure of the
f-electron magnetic interactions of CeCoIn5. Then, by solving the
superconducting gap equations on the two heavy-fermion bands
with these magnetic interactions as mediators of the
Cooper pairing, we derive a series of quantitative predictions about the
superconductive state. The agreement found between these diverse predictions
and the measured characteristics of superconducting CeCoIn5, then provides
direct evidence that the heavy-fermion Cooper pairing is indeed mediated by the
f-electron magnetism.Comment: 19 pages, 4 figures, Supplementary Information: 31 pages, 5 figure
Anisotropy in magnetic and transport properties of Fe1-xCoxSb2
Anisotropic magnetic and electronic transport measurements were carried out
on large single crystals of Fe1-xCoxSb2 (0<= x <=1). The semiconducting state
of FeSb2 evolves into metallic and weakly ferromagnetic by substitution of Fe
with Co for x<0.5. Further doping induces structural transformation from
orthorhombic Pnnm structure of FeSb2 to monoclinic P21/c structure of CoSb2
where semiconducting and diamagnetic ground state is restored again. Large
magnetoresistance and anisotropy in electronic transport were observed.Comment: 7 pages, 6 figure
Magnetic field splitting of the spin-resonance in CeCoIn5
Neutron scattering in strong magnetic fields is used to show the
spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The
underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two
modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A
linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T,
near the critical field for the incommensurate "Q-phase" indicating that the
Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure
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