5,348 research outputs found
An equivalent expression of Z2 Topological Invariant for band insulators using Non-Abelian Berry's connection
We introduce a new expression for the Z2 topological invariant of band
insulators using non- Abelian Berry's connection. Our expression can identify
the topological nature of a general band insulator without any of the gauge
fixing problems that plague the concrete implementation of previous invariants.
The new expression can be derived from the "partner switching" of the Wannier
function center during time reversal pumping and is thus equivalent to the Z2
topological invariant proposed by Kane and Mele.Comment: 14 pages, 8 figure
Role of in the reaction near threshold
The role of the resonance in the reaction near threshold is studied within an effective Lagrangian
approach. We perform a calculation for the total and differential cross section
of the reaction by including the contributions
from the intermediate state decaying into
dominated by and mesons exchanges, the nucleon pole and
resonance decaying into dominated by exchanges of
and mesons. Besides, the non-resonance process and contact terms
to keep the total scattering amplitude gauge invariant are also considered.
With our model parameters, the total cross section of this reaction is of the
order of nanobarn at photon beam energy GeV. It is
expected that our model predictions could be tested by future experiments.Comment: Published versio
Nuclear suppression of meson yields with large at the RHIC and the LHC
We calculate meson transverse momentum spectra in p+p collisions as
well as their nuclear suppressions in central A+A collisions both at the RHIC
and the LHC in LO and NLO with the QCD-improved parton model. We have included
the parton energy loss effect in hot/dense QCD medium with the effectively
medium-modified fragmentation functions in the higher-twist approach of
jet quenching. The nuclear modification factors of meson in central
Au+Au collisions at the RHIC and central Pb+Pb collisions at the LHC are
provided, and a nice agreement of our numerical results at NLO with the ALICE
measurement is observed. Predictions of yield ratios of neutral mesons such as
, and at large in relativistic
heavy-ion collisions are also presented for the first time.Comment: 7 pages, 8 figure
Berry phase effect in anomalous thermoelectric transport
We develop a theory of Berry phase effect in anomalous transport in
ferromagnets driven by statistical forces such as the gradient of temperature
or chemical potential. Here a charge Hall current arises from the Berry phase
correction to the orbital magnetization rather than from the anomalous velocity
which does not exist in the absence of a mechanical force. A finite-temperature
formula for the orbital magnetization is derived, which enables us to provide
an explicit expression for the off-diagonal thermoelectric conductivity, to
establish the Mott relation between the anomalous Nernst and Hall effects, and
to reaffirm the Onsager relations between reciprocal thermoelectric
conductivities. A first-principles evaluation of our expression is carried out
for the material CuCrSeBr, obtaining quantitative agreement
with a recent experiment.Comment: Published version in PR
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