58,842 research outputs found
Topological Anderson Insulator
Disorder plays an important role in two dimensions, and is responsible for
striking phenomena such as metal insulator transition and the integral and
fractional quantum Hall effects. In this paper, we investigate the role of
disorder in the context of the recently discovered topological insulator, which
possesses a pair of helical edge states with opposing spins moving in opposite
directions and exhibits the phenomenon of quantum spin Hall effect. We predict
an unexpected and nontrivial quantum phase termed "topological Anderson
insulator," which is obtained by introducing impurities in a two-dimensional
metal; here disorder not only causes metal insulator transition, as
anticipated, but is fundamentally responsible for creating extended edge
states. We determine the phase diagram of the topological Anderson insulator
and outline its experimental consequences.Comment: 4 pages, 4 figure
Effect of stoichiometry on oxygen incorporation in MgB2 thin films
The amount of oxygen incorporated into MgB2 thin films upon exposure to
atmospheric gasses is found to depend strongly on the material's stoichiometry.
Rutherford backscattering spectroscopy was used to monitor changes in oxygen
incorporation resulting from exposure to: (a) ambient atmosphere, (b) humid
atmospheres, (c) anneals in air and (d) anneals in oxygen. The study
investigated thin-film samples with compositions that were systematically
varied from Mg0.9B2 to Mg1.1B2. A significant surface oxygen contamination was
observed in all of these films. The oxygen content in the bulk of the film, on
the other hand, increased significantly only in Mg rich films and in films
exposed to humid atmospheres.Comment: 10 pages, 6 figures, 1 tabl
Effects of Capping on the (Ga,Mn)As Magnetic Depth Profile
Annealing can increase the Curie temperature and net magnetization in
uncapped (Ga,Mn)As films, effects that are suppressed when the films are capped
with GaAs. Previous polarized neutron reflectometry (PNR) studies of uncapped
(Ga,Mn)As revealed a pronounced magnetization gradient that was reduced after
annealing. We have extended this study to (Ga,Mn)As capped with GaAs. We
observe no increase in Curie temperature or net magnetization upon annealing.
Furthermore, PNR measurements indicate that annealing produces minimal
differences in the depth-dependent magnetization, as both as-grown and annealed
films feature a significant magnetization gradient. These results suggest that
the GaAs cap inhibits redistribution of interstitial Mn impurities during
annealing.Comment: 12 pages, 3 figures, submitted to Applied Physics Letter
The emerging roles and therapeutic potential of cyclin-dependent kinase 11 (CDK11) in human cancer.
Overexpression and/or hyperactivation of cyclin-dependent kinases (CDKs) are common features of most cancer types. CDKs have been shown to play important roles in tumor cell proliferation and growth by controlling cell cycle, transcription, and RNA splicing. CDK4/6 inhibitor palbociclib has been recently approved by the FDA for the treatment of breast cancer. CDK11 is a serine/threonine protein kinase in the CDK family and recent studies have shown that CDK11 also plays critical roles in cancer cell growth and proliferation. A variety of genetic and epigenetic events may cause universal overexpression of CDK11 in human cancers. Inhibition of CDK11 has been shown to lead to cancer cell death and apoptosis. Significant evidence has suggested that CDK11 may be a novel and promising therapeutic target for the treatment of cancers. This review will focus on the emerging roles of CDK11 in human cancers, and provide a proof-of-principle for continued efforts toward targeting CDK11 for effective cancer treatment
Complete relativistic equation of state for neutron stars
We construct the equation of state (EOS) in a wide density range for neutron
stars using the relativistic mean field theory. The properties of neutron star
matter with both uniform and non-uniform distributions are studied
consistently. The inclusion of hyperons considerably softens the EOS at high
densities. The Thomas-Fermi approximation is used to describe the non-uniform
matter, which is composed of a lattice of heavy nuclei. The phase transition
from uniform matter to non-uniform matter occurs around ,
and the free neutrons drip out of nuclei at about $2.4 \times 10^{-4}\
\rm{fm^{-3}}$. We apply the resulting EOS to investigate the neutron star
properties such as maximum mass and composition of neutron stars.Comment: 23 pages, REVTeX, 9 ps figures, to appear in Phys. Rev.
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