782 research outputs found
Functional renormalization group and variational Monte Carlo studies of the electronic instabilities in graphene near 1/4 doping
We study the electronic instabilities of near 1/4 electron doped graphene
using the functional renormalization group (FRG) and variational Monte-Carlo
method. A modified FRG implementation is utilized to improve the treatment of
the von Hove singularity. At 1/4 doping the system is a chiral spin density
wave state exhibiting the anomalous quantized Hall effect, or equivalently a
Chern insulator. When the doping deviates from 1/4, the
Cooper pairing becomes the leading instability. Our results suggest near 1/4
electron or hole doped graphene is a fertile playground for the search of Chern
insulators and superconductors.Comment: 7 pages, 8 figures, with technical details, published versio
Finite time decoherence could be suppressed efficiently in photonic crystal
The decoherence of two initially entangled qubits in anisotropic band gap
photonic crystal has been studied analytically without Born or Markovian
approximation. It is shown that the decoherence dynamics of two qubits in
photonic crystal is greatly different from that of two qubits in vacuum or
subjected to usual non-Markovian reservoir. The results also show that the
finite time decoherence invoked by spontaneous emission could be suppressed
efficiently and the entanglement of the Bell state possesses odd parity is more
easily preserved in photonic crystal than that of the Bell state possesses even
parity under the same condition. A store scheme for entangled particle pair is
proposed.Comment: 4 pages, 7 figure
Stator vibration of generator under SAERISC faults
This paper analyzes the stator vibration response under static air-gap eccentricity and rotor inter-turn short circuit composite faults (SAERISC). The detailed formula of the magnetic force on stator is firstly deduced. Then the finite element simulations and practical experiments are taken to investigate the stator vibration response. It’s shown that, 1st to 4th stator vibrations will be produced. The development of the short circuit will decrease the 2nd vibration but increase the 4th vibration, while the increment of the eccentricity will increase the 1st to 4th vibrations at the same time
Decoherence of two qubits in a non-Markovian reservoir without rotating-wave approximation
The decoherence of two initially entangled qubits in a non-Markovian
reservoir has been investigated exactly without Born Markovian approximation
and rotating-wave approximation(RWA). The non-perturbative quantum master
equation is derived and its exact solution is obtained. The decoherence
behaviors of two qubits, initially entangled in Bell states, has been
investigated in three different cases of parameters. The results show that the
counter-rotating wave terms have great influence on the decoherence behavior,
and there are differences between the exact solution of the Hamiltonian with
RWA and that of the exact Hamiltonian without RWA. It might be improper to take
RWA when the atom is in a non-markovian reservoir
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