24,755 research outputs found
Quasi-particle scattering and protected nature of topological states in a parent topological insulator BiSe
We report on angle resolved photoemission spectroscopic studies on a parent
topological insulator (TI), BiSe. The line width of the spectral
function (inverse of the quasi-particle lifetime) of the topological metallic
(TM) states shows an anomalous behavior. This behavior can be reasonably
accounted for by assuming decay of the quasi-particles predominantly into bulk
electronic states through electron-electron interaction and defect scattering.
Studies on aged surfaces reveal that topological metallic states are very much
unaffected by the potentials created by adsorbed atoms or molecules on the
surface, indicating that topological states could be indeed protected against
weak perturbations.Comment: accepted for publication in Phys. Rev. B(R
Experimental observation of hidden Berry curvature in inversion-symmetric bulk 2H-WSe2
We investigate the hidden Berry curvature in bulk 2H-WSe2 by utilizing the
surface sensitivity of angle resolved photoemission (ARPES). The symmetry in
the electronic structure of transition metal dichalcogenides is used to
uniquely determine the local orbital angular momentum (OAM) contribution to the
circular dichroism (CD) in ARPES. The extracted CD signals for the K and K'
valleys are almost identical but their signs, which should be determined by the
valley index, are opposite. In addition, the sign is found to be the same for
the two spin-split bands, indicating that it is independent of spin state.
These observed CD behaviors are what are expected from Berry curvature of a
monolayer of WSe2. In order to see if CD-ARPES is indeed representative of
hidden Berry curvature within a layer, we use tight binding analysis as well as
density functional calculation to calculate the Berry curvature and local OAM
of a monolayer WSe2. We find that measured CD-ARPES is approximately
proportional to the calculated Berry curvature as well as local OAM, further
supporting our interpretation.Comment: 6 pages, 3 figure
Bundling and Joint Marketing by Rival Firms
We study joint marketing by firms who price discriminate between consumers who patronize only one firm (single purchasers) and those who purchase from both (bundle purchasers). Firms either set the price of the bundle and then compete along side the bundle; or they determine a rebate that is applied to joint purchasers and then set prices. Even though the pricing structure in the joint marketing scheme is determined noncooperatively, the commitment to the joint marketing agreement allows firms to leverage their stand-alone prices—leading to higher profits and lower consumer surplus in either case, compared to both uniform pricing and independent price discrimination without a joint marketing agreement. Nevertheless the two schemes differ dramatically, in that rebates increase joint purchasing, whereas bundle pricing diminishes bundle purchases
using HYP-smeared staggered fermions in unquenched QCD
We present results for kaon mixing parameter calculated using
HYP-smeared improved staggered fermions on the MILC asqtad lattices. We use
three lattice spacings (, and fm), ten different
valence quark masses (), and several light sea-quark
masses in order to control the continuum and chiral extrapolations. We derive
the next-to-leading order staggered chiral perturbation theory (SChPT) results
necessary to fit our data, and use these results to do extrapolations based
both on SU(2) and SU(3) SChPT. The SU(2) fitting is particularly
straightforward because parameters related to taste-breaking and matching
errors appear only at next-to-next-to-leading order. We match to the continuum
renormalization scheme (NDR) using one-loop perturbation theory. Our final
result is from the SU(2) analysis, with the SU(3) result providing a (less
accurate) cross check. We find and ,
where the first error is statistical and the second systematic. The error is
dominated by the truncation error in the matching factor. Our results are
consistent with those obtained using valence domain-wall fermions on lattices
generated with asqtad or domain-wall sea quarks.Comment: 37 pages, 31 figures, most updated versio
Deficiency of Capicua disrupts bile acid homeostasis
Capicua (CIC) has been implicated in pathogenesis of spinocerebellar ataxia type 1 and cancer in mammals; however, the in vivo physiological functions of CIC remain largely unknown. Here we show that Cic hypomorphic (Cic-L-/-) mice have impaired bile acid (BA) homeostasis associated with induction of proinflammatory cytokines. We discovered that several drug metabolism and BA transporter genes were down-regulated in Cic-L-/- liver, and that BA was increased in the liver and serum whereas bile was decreased within the gallbladder of Cic-L-/- mice. We also found that levels of proinflammatory cytokine genes were up-regulated in Cic-L-/- liver. Consistent with this finding, levels of hepatic transcriptional regulators, such as hepatic nuclear factor 1 alpha (HNF1 alpha), CCAAT/enhancer-binding protein beta (C/EBP beta), forkhead box protein A2 (FOXA2), and retinoid X receptor alpha (RXR alpha), were markedly decreased in Cic-L-/- mice. Moreover, induction of tumor necrosis factor alpha (Tnf alpha) expression and decrease in the levels of FOXA2, C/EBP beta, and RXRa were found in Cic-L-/- liver before BA was accumulated, suggesting that inflammation might be the cause for the cholestasis in Cic-L-/- mice. Our findings indicate that CIC is a critical regulator of BA homeostasis, and that its dysfunction might be associated with chronic liver disease and metabolic disorders.open11810Ysciescopu
Effective Vortex Mass from Microscopic Theory
We calculate the effective mass of a single quantized vortex in the BCS
superconductor at finite temperature. Based on effective action approach, we
arrive at the effective mass of a vortex as integral of the spectral function
divided by over frequency. The spectral function is
given in terms of the quantum-mechanical transition elements of the gradient of
the Hamiltonian between two Bogoliubov-deGennes (BdG) eigenstates. Based on
self-consistent numerical diagonalization of the BdG equation we find that the
effective mass per unit length of vortex at zero temperature is of order (=Fermi momentum, =coherence length), essentially
equaling the electron mass displaced within the coherence length from the
vortex core. Transitions between the core states are responsible for most of
the mass. The mass reaches a maximum value at and decreases
continuously to zero at .Comment: Supercedes prior version, cond-mat/990312
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