715 research outputs found
The quasiparticle band gap in the topological insulator Bi2Te3
We present a theoretical study of dispersion of states which form the bulk
band-gap edges in the three-dimensional topological insulator Bi2Te3. Within
density functional theory, we analyze the effect of atomic positions varying
within the error range of the available experimental data and approximation
chosen for the exchange-correlation functional on the bulk band gap and k-space
location of valence- and conduction-band extrema. For each set of the positions
with different exchange-correlation functionals, we show how many-body
corrections calculated within a one-shot GW approach affect the mentioned
characteristics of electronic structure of Bi2Te3. We thus also illustrate to
what degree the one-shot GW results are sensitive to the reference one-particle
band structure in the case of bismuth telluride. We found that for this
topological insulator the GW corrections enlarge the fundamental band gap and
for certain atomic positions and reference band structure bring its value in
close agreement with experiment.Comment: 12 pages, 6 figures, 5 table
Planar diagrams from optimization
We propose a new toy model of a heteropolymer chain capable of forming planar
secondary structures typical for RNA molecules. In this model the sequential
intervals between neighboring monomers along a chain are considered as quenched
random variables. Using the optimization procedure for a special class of
concave--type potentials, borrowed from optimal transport analysis, we derive
the local difference equation for the ground state free energy of the chain
with the planar (RNA--like) architecture of paired links. We consider various
distribution functions of intervals between neighboring monomers (truncated
Gaussian and scale--free) and demonstrate the existence of a topological
crossover from sequential to essentially embedded (nested) configurations of
paired links.Comment: 10 pages, 10 figures, the proof is added. arXiv admin note: text
overlap with arXiv:1102.155
- …