38,899 research outputs found
Magnetoconductivity in Weyl semimetals: Effect of chemical potential and temperature
We present the detailed analyses of magneto-conductivities in a Weyl
semimetal within Born and self-consistent Born approximations. In the presence
of the charged impurities, the linear magnetoresistance can happen when the
charge carriers are mainly from the zeroth (n=0) Landau level. Interestingly,
the linear magnetoresistance is very robust against the change of temperature,
as long as the charge carriers mainly come from the zeroth Landau level. We
denote this parameter regime as the high-field regime. On the other hand, the
linear magnetoresistance disappears once the charge carriers from the higher
Landau levels can provide notable contributions. Our analysis indicates that
the deviation from the linear magnetoresistance is mainly due to the deviation
of the longitudinal conductivity from the behavior. We found two
important features of the self-energy approximation: 1. a dramatic jump of
, when the Landau level begins to contribute charge
carriers, which is the beginning point of the middle-field regime, when
decreasing the external magnetic field from high field; 2. In the low-field
regime shows a behavior and results the
magnetoresistance to show a behavior. The detailed and
careful numerical calculation indicates that the self-energy approximation
(including both the Born and the self-consistent Born approximations) does not
explain the recent experimental observation of linear magnetoresistance in Weyl
semimetals.Comment: The accepted version. Extending the previous version by including the
discussions of self-consistent Born approximatio
Identification of the major cause of endemically poor mobilities in SiC/SiO2 structures
Materials with good carrier mobilities are desired for device applications,
but in real devices the mobilities are usually limited by the presence of
interfaces and contacts. Mobility degradation at semiconductor-dielectric
interfaces is generally attributed to defects at the interface or inside the
dielectric, as is the case in Si/SiO2 structures, where processing does not
introduce detrimental defects in the semiconductor. In the case of SiC/SiO2
structures, a decade of research focused on reducing or passivating interface
and oxide defects, but the low mobilities have persisted. By invoking
theoretical results and available experimental evidence, we show that thermal
oxidation generates carbon di-interstitial defects inside the semiconductor
substrate and that they are a major cause of the poor mobility in SiC/SiO2
structures
Strong magnetic fluctuations in superconducting state of CeCoIn
We show results on the vortex core dissipation through current-voltage
measurements under applied pressure and magnetic field in the superconducting
phase of CeCoIn. We find that as soon as the system becomes
superconducting, the vortex core resistivity increases sharply as the
temperature and magnetic field decrease. The sharp increase in flux flow
resistivity is due to quasiparticle scattering on critical antiferromagnetic
fluctuations. The strength of magnetic fluctuations below the superconducting
transition suggests that magnetism is complimentary to superconductivity and
therefore must be considered in order to fully account for the low-temperature
properties of CeCoIn.Comment: 7 pages, 6 figure
Magnetization distribution and orbital moment in the non-Superconducting Chalcogenide Compound K0.8Fe1.6Se2
We have used polarized and unpolarized neutron diffraction to determine the
spatial distribution of the magnetization density induced by a magnetic field
of 9 T in the tetragonal phase of K0.8Fe1.6Se2. The maximum entropy
reconstruction shows clearly that most of the magnetization is confined to the
region around the iron atoms whereas there is no significant magnetization
associated with either Se or K atoms. The distribution of magnetization around
the Fe atom is slightly nonspherical with a shape which is extended along the
[0 0 1] direction in the projection. Multipolar refinement results show that
the electrons which give rise to the paramagnetic susceptibility are confined
to the Fe atoms and their distribution suggests that they occupy 3d t2g-type
orbitals with around 66% in those of xz/yz symmetry. Detail modeling of the
magnetic form factor indicates the presence of an orbital moment to the total
paramagnetic moment of Fe2+Comment: 7 pages, accepted for publication in Physical Review
Heavy-tailed statistics in short-message communication
Short-message (SM) is one of the most frequently used communication channels
in the modern society. In this Brief Report, based on the SM communication
records provided by some volunteers, we investigate the statistics of SM
communication pattern, including the interevent time distributions between two
consecutive short messages and two conversations, and the distribution of
message number contained by a complete conversation. In the individual level,
the current empirical data raises a strong evidence that the human activity
pattern, exhibiting a heavy-tailed interevent time distribution, is driven by a
non-Poisson nature.Comment: 4 pages, 4 figures and 1 tabl
Coupling methods for continuum model with molecular model
Coupling methods for continuum models with molecular models are developed. Two methods are studied here: an overlapping domain decomposition method, which has overlapping domain, and an edge-to-edge decomposition method, which has an interface between two models. These two methods enforce the compatibility on the overlapping domain or interface nodes/atoms by the Lagrange multiplier method or the augmented Lagrangian method. 1
- …