1,917 research outputs found
Electronic structure of YbB: Is it a Topological Insulator or not?
To resolve the controversial issue of the topological nature of the
electronic structure of YbB, we have made a combined study using density
functional theory (DFT) and angle resolved photoemission spectroscopy (ARPES).
Accurate determination of the low energy band topology in DFT requires the use
of modified Becke-Johnson exchange potential incorporating the spin-orbit
coupling and the on-site Coulomb interaction of Yb electrons as large
as 7 eV. We have double-checked the DFT result with the more precise GW band
calculation. ARPES is done with the non-polar (110) surface termination to
avoid band bending and quantum well confinement that have confused ARPES
spectra taken on the polar (001) surface termination. Thereby we show
definitively that YbB has a topologically trivial B 2-Yb 5
semiconductor band gap, and hence is a non-Kondo non-topological insulator
(TI). In agreement with theory, ARPES shows pure divalency for Yb and a -
band gap of 0.3 eV, which clearly rules out both of the previous scenarios of
- band inversion Kondo TI and - band inversion non-Kondo TI. We
have also examined the pressure-dependent electronic structure of YbB,
and found that the high pressure phase is not a Kondo TI but a
\emph{p}-\emph{d} overlap semimetal.Comment: The main text is 6 pages with 4 figures, and the supplementary
information contains 6 figures. 11 pages, 10 figures in total To be appeared
in Phys. Rev. Lett. (Online publication is around March 16 if no delays.
A Survey on Centrality Metrics and Their Implications in Network Resilience
Centrality metrics have been used in various networks, such as communication,
social, biological, geographic, or contact networks. In particular, they have
been used in order to study and analyze targeted attack behaviors and
investigated their effect on network resilience. Although a rich volume of
centrality metrics has been developed for decades, a limited set of centrality
metrics have been commonly in use. This paper aims to introduce various
existing centrality metrics and discuss their applicabilities and performance
based on the results obtained from extensive simulation experiments to
encourage their use in solving various computing and engineering problems in
networks.Comment: Main paper: 36 pages, 2 figures. Appendix 23 pages,45 figure
Transport properties of graphene with one-dimensional charge defects
We study the effect of extended charge defects in electronic transport
properties of graphene. Extended defects are ubiquitous in chemically and
epitaxially grown graphene samples due to internal strains associated with the
lattice mismatch. We show that at low energies these defects interact quite
strongly with the 2D Dirac fermions and have an important effect in the
DC-conductivity of these materials.Comment: 6 pages, 5 figures. published version: one figure, appendix and
references adde
Recommended from our members
Mechanism and treatment for learning and memory deficits in mouse models of Noonan syndrome.
In Noonan syndrome (NS) 30-50% of subjects show cognitive deficits of unknown etiology and with no known treatment. Here, we report that knock-in mice expressing either of two NS-associated mutations in Ptpn11, which encodes the nonreceptor protein tyrosine phosphatase Shp2, show hippocampal-dependent impairments in spatial learning and deficits in hippocampal long-term potentiation (LTP). In addition, viral overexpression of an NS-associated allele PTPN11(D61G) in adult mouse hippocampus results in increased baseline excitatory synaptic function and deficits in LTP and spatial learning, which can be reversed by a mitogen-activated protein kinase kinase (MEK) inhibitor. Furthermore, brief treatment with lovastatin reduces activation of the GTPase Ras-extracellular signal-related kinase (Erk) pathway in the brain and normalizes deficits in LTP and learning in adult Ptpn11(D61G/+) mice. Our results demonstrate that increased basal Erk activity and corresponding baseline increases in excitatory synaptic function are responsible for the LTP impairments and, consequently, the learning deficits in mouse models of NS. These data also suggest that lovastatin or MEK inhibitors may be useful for treating the cognitive deficits in NS
- …