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Search Results: 1 - 10 of 57789 matches for " Zhen-Guo Fu "
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Some weakly mappings on intuitionistic fuzzy topological spaces
Zhen-Guo Xu,Fu-Gui Shi
Tamkang Journal of Mathematics , 2008, DOI: 10.5556/j.tkjm.39.2008.25-32
Abstract: In this paper, we shall introduce concepts of fuzzy semiopen set, fuzzy semiclosed set, fuzzy semiinterior, fuzzy semiclosure on intuitionistic fuzzy topological space and fuzzy open (fuzzy closed) mapping, fuzzy irresolute mapping, fuzzy irresolute open (closed) mapping, fuzzy semicontinuous mapping and fuzzy semiopen (semiclosed) mapping between two intuitionistic fuzzy topological spaces. Moreover, we shall discuss their some properties.
SP-convergence in $L$-topological spaces
Zhen-Guo Xu,Fu-Gui Shi
Tamkang Journal of Mathematics , 2007, DOI: 10.5556/j.tkjm.38.2007.139-151
Abstract: In this paper, SP-convergence theory of nets, ideals and filters are built by means of the concept of strongly preclosed $L$-sets. Their applications are presented.
Excitonic condensation for the surface states of topological insulator bilayers
Zhigang Wang,Ningning Hao,Zhen-Guo Fu,Ping Zhang
Physics , 2011, DOI: 10.1088/1367-2630/14/6/063010
Abstract: We propose a generic topological insulator bilayer (TIB) system to study the excitonic condensation with self-consistent mean-field (SCMF) theory. We show that the TIB system presents the crossover behavior from the Bardeen-Cooper-Schrieffer (BCS) limit to Bose-Einstein condensation (BEC) limit. Moreover, by comparison with traditional semiconductor systems, we find that for the present system the superfluid property in the BEC phase is more sensitive to electron-hole density imbalance and the BCS phase is more robust. Applying this TIB model into Bi$_{2}$Se$_{3}$-family material, we find that the BEC phase is most probable to be observed in experiment. We also calculate the critical temperature for Bi$_{2}$Se$_{3}$-family TIB system, which is $\mathtt{\sim}100$ K. More interestingly, we can expect this relative high-temperature excitonic condensation since our calculated SCMF critical temperature is approximately equal to the Kosterlitz-Thouless transition temperature.
Probing crossover from analogous weak antilocalization to localization by an Aharonov-Bohm interferometer on topological insulator surface
Zhen-Guo Fu,Ping Zhang,Shu-Shen Li
Physics , 2011, DOI: 10.1063/1.3697993
Abstract: We propose a scanning tunneling microscopy Aharonov-Bohm (AB) interferometer on the surface of a topological insulator (TI) to probe the crossover from analogous weak antilocalization (WAL) to weak localization (WL) phenomenon via the AB oscillations in spin-resolved local density of states (LDOS). Based on our analytical and numerical results, we show that with increasing the energy gap of TI surface states, the $\Phi_{0}/2$=$hc/2e$ periodic AB oscillations in spin-resolved LDOS gradually transit into the $\Phi_{0}$ periodic oscillations.
The effect of the warping term on the fractional quantum Hall states in topological insulators
Fawei Zheng,Zhigang Wang,Zhen-Guo Fu,Ping Zhang
Physics , 2013,
Abstract: The warping effect on the fractional quantum Hall (FQH) states in topological insulators is studied theoretically. Based on the perturbed wavefunctions, which include contributions from the warping term, analytical expressions for Haldane's pseudopotentials are obtained. We show that the warping term does not break the symmetry of the pseudopotentials for $n$=$\pm1$ Landau levels (LLs). With increasing the warping strength of the Fermi surface, our results indicate that the stability of the FQH states for LL $n=0$ (LLs $n$=$\pm1$) becomes stronger (weaker), and the excitation gap at $\nu=1/3$ FQH state for LL $n$=0 also increases while the gaps for LLs $n$=$\pm1$ are unchanged.
Fractional quantum Hall effect of topological surface states under a strong tilted magnetic field
Fawei Zheng,Zhigang Wang,Zhen-Guo Fu,Ping Zhang
Physics , 2013, DOI: 10.1209/0295-5075/103/27001
Abstract: The fractional quantum Hall effect (FQHE) of topological surface-state particles under a tilted strong magnetic field is theoretically studied by using the exact diagonalization method. The Haldane's pseudopotentials for the Coulomb interaction are analytically obtained. The results show that by increasing the in-plane component of the tilted magnetic field, the FQHE state at $n$=0 Landau level (LL) becomes more stable, while the stabilities of $n$=$\pm1$ LLs become weaker. Moreover, we find that the excitation gaps of the $\nu=1/3$ FQHE states increase as the tilt angle is increased.
Aharonov-Bohm oscillations in the local density of topological surface states
Zhen-Guo Fu,Ping Zhang,Shu-Shen Li
Physics , 2011, DOI: 10.1063/1.3669506
Abstract: We study Aharonov-Bohm (AB) oscillations in the local density of states (LDOS) for topological insulator (TI) and conventional metal Au(111) surfaces with spin-orbit interaction, which can be probed by spin-polarized scanning tunneling microscopy. We show that the spacial AB oscillatory period in the total LDOS is a flux quantum $\Phi_{0}\mathtt{=}hc/e$ (weak localization) in both systems. Remarkably, an analogous weak antilocalization with $\Phi_{0}/2$ periodic spacial AB oscillations in spin components of LDOS for TI surface is observed, while it is absent in Au(111).
Superfluidity and effective mass of magnetoexcitons in topological insulator bilayers: Effect of inter-Landau-level Coulomb interaction
Zhigang Wang,Zhen-Guo Fu,Ping Zhang
Physics , 2012, DOI: 10.1209/0295-5075/98/47002
Abstract: The effective mass and superfluidity-normal phase transition temperature of magnetoexcitons in topological insulator bilayers are theoretically investigated. The intra-Landau-level Coulomb interaction is treated perturbatively, from which the effective magnetoexciton mass is analytically discussed. The inclusion of inter-Landau-level Coulomb interaction by more exact numerical diagonalization of the Hamiltonian brings out important modifications to magnetoexciton properties, which are specially characterized by prominent reduction in the magnetoexciton effective mass and promotion in the superfluidity-normal phase transition temperature at a wide range of external parameters.
Pseudo-magnetoexcitons in strained graphene bilayers without external magnetic fields
Zhigang Wang,Zhen-Guo Fu,Fawei Zheng,Ping Zhang
Physics , 2012, DOI: 10.1103/PhysRevB.87.125418
Abstract: The structural and electronic properties of graphene leads its charge carriers to behave like relativistic particles, which is described by a Dirac-like Hamiltonian. Since graphene is a monolayer of carbon atoms, the strain due to elastic deformations will give rise to so-called `pseudomagnetic fields (PMF)' in graphene sheet, and that has been realized experimentally in strained graphene sample. Here we propose a realistic strained graphene bilayer (SGB) device to detect the pseudo-magnetoexcitons (PME) in the absence of external magnetic field. The carriers in each graphene layer suffer different strong PMFs due to strain engineering, which give rise to Landau quantization. The pseudo-Landau levels (PLLs) of electron-hole pair under inhomogeneous PMFs in SGB are analytically obtained in the absence of Coulomb interactions. Based on the general analytical optical absorption selection rule for PME, we show that the optical absorption spectrums can interpret the corresponding formation of Dirac-type PME. We also predict that in the presence of inhomogeneous PMFs, the superfluidity-normal phase transition temperature of PME is greater than that under homogeneous PMFs.}
Magnetoexcitons and optical absorption of bilayer-structured topological insulators
Zhigang Wang,Zhen-Guo Fu,Ping Zhang
Physics , 2012, DOI: 10.1063/1.4704657
Abstract: Optical absorption properties of magnetoexcitons in topological insulator bilayers under a strong magnetic field are theoretically studied. A general analytical formula of optical absorption selection rule is obtained in the noninteracting as well as Coulomb intra-Landau-level interacting cases, which remarkably helps to interpret the resonant peaks in absorption spectroscopy and the corresponding formation of Dirac-type magnetoexcitons. We also discuss the optical absorption spectroscopy of magnetoexcitons in the presence of inter-Landau-level Coulomb interaction, which becomes more complex. Our results could be detected in the magneto-optical experiments.
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