Electronic transport of bilayer graphene with asymmetry line defects

In this paper,we study the quantum properties of a bilayer graphene with(asymmetry) line defects.The localized states are found around the line defects.Thus,the line defects on one certain layer of the bilayer graphene can lead to an electric transport channel.By adding a bias potential along the direction of the line defects,we calculate the electric conductivity of bilayer graphene with line defects using the Landauer-Biittiker theory,and show that the channel affects the electric conductivity remarkably by comparing the results with those in a perfect bilayer graphene.This one-dimensional line electric channel has the potential to be applied in nanotechnology engineering.     

PARISI-SOURLAS CONFINEMENT MECHANISM OF QUANTUM CHROMODYNAMICS

Using Parisi and Sourlas dimensional reduction, four-dimensional quantum chromodynamics is reduced to a two-dimensional principal chiral model by suitable superspace embedding. The frame T^a cannot be regarded as a fixed one and the frame connection field \varω_μ(x) becomes a dynamical gauge field in two dimensions, giving rise to a confining potential. As a result of the original SU(3) Yang-Mills field obtains another SU(3) local symmetry and turns into SU(3)×SU(3) local symmetry－one group element as exp (iδ\varphi^aT^a) with fixed frame T^a, the other gauging the frame T^a.     

An Extended Effective Potential Method with Topological Phase of Spin Tunnelling

An extended effective potential(EEP)method is proposed to calculate the spin tunnelling splitting of a single domain ferromagnetic grain.By adding a phase factor to replace the boundary conditioin,the new method is not only accurate but also topological effects.In the large spin limit,the results from the spin-coherent-state path integral have systematic disparity with numerical studies,while those from the EEP method agree well with numerical studies.     

A Possible Explanation to Paradox in Horse Spleen Ferritins

There are contradicting opinions about the tunnelling experiments in horse-spleen ferritin particles.By distinguish the coherent and incoherent tunnelling processes,we give a unified explanation to different experiments.As a rsult,a possible explanation to the paradox is proposed.     

Controlled Phase Flip Gate and Its Application in Low-Q Cavities by Single-Photon Input-Output Process

By employing an auxiliary cavity, we investigate the possibility to implement the conditional phase flip (CPF) gate on two atoms confined in separate low-Q cavities by single-photon input-output process, based on the Faraday rotation. This indicates a universal quantum computing available with sophisticated cavity QED techniques. As examples, we carry out generation of cluster states of distant atomic qubits and accomplish a teleportation based on Bell-state measurement in low-Q cavities.     

Fermion Bound States Around Skyrmions in Doped Antiferromagnets

We show the skyrmion effects in doped antiferromagnets for the uniform flux phase. The low-energy effective theory of the t‘ - J model can be mapped onto the massive quantum electrodynamics. There exist Fermion bound states around skyrmions. For each sublattice, there exist induced fractional fermion numbers around the skyrmions. The total induced fermion number is zero due to the “cancelling effect“ between two sublattices with Opposite charges.     

Bogoliubov excitations in a Bose–Hubbard model on a hyperhoneycomb lattice

We study the topological properties of Bogoliubov excitation modes in a Bose–Hubbard model of three-dimensional(3 D) hyperhoneycomb lattices. For the non-interacting case, there exist nodal loop excitations in the Bloch bands. As the on-site repulsive interaction increases, the system is first driven into the superfluid phase and then into the Mott-insulator phase. In both phases, the excitation bands exhibit robust nodal-loop structures and bosonic surface states. From a topology point of view, these nodal-loop excitation modes may be viewed as a permanent fingerprint left in the Bloch bands.     

CROSSOVER FROM THERMAL HOPPING TO QUANTUM TUNNELING IN FERROMAGNETIC PARTICLE

The crossover from thermal hopping to quantum tunneling is studied. We show that the decay rate Γ with dissipation can accurately be determined near the crossover temperature. Besides considering the Wentzel-Kramers-Brillo uin exponent, we also calculate contribution of the fluctuation modes around the saddle point and give an extended account of a previous study of crossover region. We deal with two dangerous fluctuation modes whose contribution cannot be calculated by the steepest descent method and show that higher order couplings between the two dangerous modes need to be taken into consideration.     

The relationship between four-dimensional θ=π Yang－Mills theory and the two-dimensional Wess－Zumino－Novikov－Witten model

Used the dimensional reduction in the sense of Parisi and Sourlas, the gauge fixing term of the four-dimensional Yang－Mills field without the theta term is reduced to a two-dimensional principal chiral model. By adding the θ term (θ=π), the two-dimensional principal chiral model changes into the two-dimensional level 1 Wess－Zumino－Novikov－Witten model. The non-trivial fixed point indicates that Yang－Mills theory at θ=π is a critical theory without mass gap and confinement.     

Topological hierarchy matters — topological matters with superlattices of defects

Topological insulators/superconductors are new states of quantum matter with metallic edge/surface states.In this paper,we review the defects effect in these topological states and study new types of topological matters — topological hierarchy matters.We find that both topological defects(quantized vortices) and non topological defects(vacancies) can induce topological mid-gap states in the topological hierarchy matters after considering the superlattice of defects.These topological mid-gap states have nontrivial topological properties,including the nonzero Chern number and the gapless edge states.Effective tight-binding models are obtained to describe the topological mid-gap states in the topological hierarchy matters.