2,805 research outputs found
Stable nontrivial Z2 topology in ultrathin Bi (111) films: a first-principles study
Recently, there have been intense efforts in searching for new topological
insulator (TI) materials. Based on first-principles calculations, we find that
all the ultrathin Bi (111) films are characterized by a nontrivial Z2 number
independent of the film thickness, without the odd-even oscillation of
topological triviality as commonly perceived. The stable nontrivial Z2 topology
is retained by the concurrent band gap inversions at multiple
time-reversal-invariant k-points and associated with the intermediate
inter-bilayer coupling of the multi-bilayer Bi film. Our calculations further
indicate that the presence of metallic surface states in thick Bi(111) films
can be effectively removed by surface adsorption.Comment: 5 pages, 3 figure
Reconsideration of the QCD corrections to the decays into light hadrons using the principle of maximum conformality
In the paper, we analyze the decays into light hadrons at the
next-to-leading order QCD corrections by applying the principle of maximum
conformality (PMC). The relativistic correction at the -order level has been included in the discussion, which gives about
contribution to the ratio . The PMC, which satisfies the renormalization
group invariance, is designed to obtain a scale-fixed and scheme-independent
prediction at any fixed order. To avoid the confusion of treating -terms,
we transform the usual pQCD series into the one under the
minimal momentum space subtraction scheme. To compare with the prediction under
conventional scale setting, , after applying the PMC, we obtain
, where the
errors are squared averages of the ones caused by and . The PMC prediction agrees with the recent PDG value within errors, i.e.
. Thus we think the mismatching
of the prediction under conventional scale-setting with the data is due to
improper choice of scale, which however can be solved by using the PMC.Comment: 5 pages, 2 figure
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Rhodium-catalyzed borylative carbon monoxide reduction to gem-diborylmethane
Herein, we developed a rhodium-catalyzed reduction of CO with bis(pinacolato)diboron (B2pin2) under atmospheric pressure of CO with silane as the hydride source, gem-diborylmethane [H2C(Bpin)2] as a versatile and fundamental C1 compound can be formed. Notably, this is the first example on transition metal-catalyzed borylation of CO. © 2020 The Author(s
The leptonic decay using the principle of maximum conformality
In the paper, we study the leptonic decay width
by using the principle of maximum
conformality (PMC) scale-setting approach. The PMC adopts the renormalization
group equation to set the correct momentum flow of the process, whose value is
independent to the choice of the renormalization scale and its prediction thus
avoids the conventional renormalization scale ambiguities. Using the known
next-to-next-to-next-to-leading order perturbative series together with the PMC
single scale-setting approach, we do obtain a renormalization scale independent
decay width, keV,
where the error is squared average of those from
, GeV and the choices of
factorization scales within of their central values. To compare with
the result under conventional scale-setting approach, this decay width agrees
with the experimental value within errors, indicating the importance of a
proper scale-setting approach.Comment: 6 pages, 4 figure
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