495 research outputs found
Linear magnetoconductivity in an intrinsic topological Weyl semimetal
Searching for the signature of the violation of chiral charge conservation in
solids has inspired a growing passion on the magneto-transport in topological
semimetals. One of the open questions is how the conductivity depends on
magnetic fields in a semimetal phase when the Fermi energy crosses the Weyl
nodes. Here, we study both the longitudinal and transverse magnetoconductivity
of a topological Weyl semimetal near the Weyl nodes with the help of a two-node
model that includes all the topological semimetal properties. In the semimetal
phase, the Fermi energy crosses only the 0th Landau bands in magnetic fields.
For a finite potential range of impurities, it is found that both the
longitudinal and transverse magnetoconductivity are positive and linear at the
Weyl nodes, leading to an anisotropic and negative magnetoresistivity. The
longitudinal magnetoconductivity depends on the potential range of impurities.
The longitudinal conductivity remains finite at zero field, even though the
density of states vanishes at the Weyl nodes. This work establishes a relation
between the linear magnetoconductivity and the intrinsic topological Weyl
semimetal phase.Comment: An extended version accepted by New. J. Phys. with 15 pages and 3
figure
Edge states and integer quantum Hall effect in topological insulator thin films
The integer quantum Hall effect is a topological state of quantum matter in
two dimensions, and has recently been observed in three-dimensional topological
insulator thin films. Here we study the Landau levels and edge states of
surface Dirac fermions in topological insulators under strong magnetic field.
We examine the formation of the quantum plateaux of the Hall conductance and
find two different patterns, in one pattern the filling number covers all
integers while only odd integers in the other. We focus on the quantum plateau
closest to zero energy and demonstrate the breakdown of the quantum spin Hall
effect resulting from structure inversion asymmetry. The phase diagrams of the
quantum Hall states are presented as functions of magnetic field, gate voltage
and chemical potential. This work establishes an intuitive picture of the edge
states to understand the integer quantum Hall effect for Dirac electrons in
topological insulator thin films.Comment: 10 pages, 5 figure
High-field magnetoconductivity of topological semimetals with short-range potential
Weyl semimetals are three-dimensional topological states of matter, in a
sense that they host paired monopoles and antimonopoles of Berry curvature in
momentum space, leading to the chiral anomaly. The chiral anomaly has long been
believed to give a positive magnetoconductivity or negative magnetoresistivity
in strong and parallel fields. However, several recent experiments on both Weyl
and Dirac topological semimetals show a negative magnetoconductivity in high
fields. Here, we study the magnetoconductivity of Weyl and Dirac semimetals in
the presence of short-range scattering potentials. In a strong magnetic field
applied along the direction that connects two Weyl nodes, we find that the
conductivity along the field direction is determined by the Fermi velocity,
instead of by the Landau degeneracy. We identify three scenarios in which the
high-field magnetoconductivity is negative. Our findings show that the
high-field positive magnetoconductivity may not be a compelling signature of
the chiral anomaly and will be helpful for interpreting the inconsistency in
the recent experiments and earlier theories.Comment: An extended version accepted by Phys. Rev. B, with 11 pages and 4
figure
2,2,2-TrifluoroÂethyl 4-methylÂbenzeneÂsulfonate
In the crystal structure of the title compound, C9H9F3O3S, interÂmolecular C—H⋯O hydrogen bonds link the molÂecules along the c-axis direction. Also present are slipped π–π stacking interÂactions between phenylÂene rings, with perpendicular interÂplanar distances of 3.55 (2) Å and centroid–centroid distances of 3.851 (2) Å
Methyl 2-amino-5-chloroÂbenzoate
The title compound, C8H8ClNO2, is almost planar, with an r.m.s. deviation of 0.0410 Å from the plane through the non-hydrogen atoms. In the crystal structure, interÂmolecular N—H⋯O hydrogen bonds link the molÂecules into chains along the b axis. An intraÂmolecular N—H⋯O hydrogen bond results in the formation of a six-membered ring
The research progress on the mechanism of adenosine A1 receptor-mediated calcitonin gene-related peptide to relieve migraine
Currently, the pathogenesis of migraine is unclear. The trigeminal vascular reflex theory is the dominant pathogenesis theory, and its core parts are neurogenic inflammation and pain sensitisation. Calcitonin gene related peptide (CGRP) is the most powerful vasodilating peptide in brain circulation. It is also a marker of trigeminal nerve microvascular activation that plays a synergistic role in the pathogenesis of migraine. Adenosine A1 receptor (A1R) can inhibit the release of CGRP in the trigeminal nerve vascular system to alleviate migraine by mediating adenosine. This review summarises the progress of research on the alleviation of migraine by using A1R-mediated CGRP
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