21,562 research outputs found
Interaction induced topological phase transition in Bernevig-Hughes-Zhang model
We study interaction induced topological phase transition in
Bernevig-Hughes-Zhang model. Topological nature of the phase transition is
revealed by directly calculating the Z2 index of the interacting system from
the single-particle Green's function. The interacting Z2 index is also
consistently checked through the edge spectra. Combined with ab initio methods,
present approach is a useful tool searching for correlated topological
insulating materials from the first-principle point of view.Comment: 4.5 pages, 4 figures, reference adde
Pole expansion of self-energy and interaction effect on topological insulators
We study effect of interactions on time-reversal-invariant topological
insulators. Their topological indices are expressed by interacting Green's
functions. Under the local self-energy approximation, we connect topological
index and surface states of an interacting system to an auxiliary
noninteracting system, whose Hamiltonian is related to the pole-expansions of
the local self-energy. This finding greatly simplifies the calculation of
interacting topological indices and gives an noninteracting pictorial
description of interaction driven topological phase transitions. Our results
also bridge studies of the correlated topological insulating materials with the
practical dynamical-mean-field-theory calculations.Comment: 4.2 pages, 3 figures, reference added, typos correcte
Magnetism of Cold Fermionic Atoms on p-Band of an Optical Lattice
We carry out \textit{ab initio} study of ground state phase diagram of
spin-1/2 cold fermionic atoms within two-fold degenerate -band of an
anisotropic optical lattice. Using the Gutzwiller variational approach, we show
that a robust ferromagnetic phase exists for a vast range of band fillings and
interacting strengths. The ground state crosses over from spin density wave
state to spin-1 Neel state at half filling. Additional harmonic trap will
induce spatial separation of varies phases. We also discuss several relevant
observable consequences and detection methods. Experimental test of the results
reported here may shed some light on the long-standing issue of itinerant
ferromagnetism.Comment: 5 pages, 4 figure
Coronal magnetic topology and the production of solar impulsive energetic electrons
We investigate two candidate solar sources or active regions (ARs) in
association with a solar impulsive energetic electron (SIEE) event on 2002
October 20. The solar particle release (SPR) times of SIEEs are derived by
using their velocity dispersion with consideration of the instrumental effect.
It is found that there are double electron injections at the Sun. The
low-energy (<13 keV) electron injection coincides with a C6.6 flare in AR10154
and is accompanied with prominent type III radio bursts rather than a stronger
M1.8 flare in AR10160. The M1.8 flare produces, however, faint type III radio
bursts. Whereas electrons of 25 to 300 keV are released 9 min later when a
jet-like CME travels to 2.6 solar radii. We further examine the coronal
magnetic configurations above the two ARs based on the potential field source
surface (PFSS) model. It is found that open field lines, rooted in AR10154 and
well connected to the Earth, provide escaping channels for energetic electrons.
Only a small portion of magnetic fields are opened above AR10160, being
responsible for the faint type III radio bursts. These lines are, however, not
well connected, making it impossible for SIEEs detection by near-Earth
spacecraft. The results appear to establish a physical link between coronal
magnetic topology, formation of type III radio bursts, and production of SIEEs.Comment: A&A Letters, accepte
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