37 research outputs found

    Mode entanglement of an electron in one-dimensional determined and random potentials

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    By using the measure of concurrence, mode entanglement of an electron moving in four kinds of one-dimensional determined and random potentials is studied numerically. The extended and local- ized states can be distinguished by mode entanglement. There are sharp transitions in concurrence at mobility edges. It provides that the mode entanglement may be a new index for a metal-insulator transition.Comment: 6 pages,16 figure

    The effects of KSEA interaction on the ground-state properties of spin chains in a transverse field

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    The effects of symmetric helical interaction which is called the Kaplan, Shekhtman, Entin-Wohlman, and Aharony (KSEA) interaction on the ground-state properties of three kinds of spin chains in a transverse field have been studied by means of correlation functions and chiral order parameter. We find that the anisotropic transition of XYXY chain in a transverse field (XYXYTF) disappears because of the KSEA interaction. For the other two chains, we find that the regions of gapless chiral phases in the parameter space induced by the DM or XZYYZXXZY-YZX type of three-site interaction are decreased gradually with increase of the strength of KSEA interaction. When it is larger than the coefficient of DM or XZYYZXXZY-YZX type of three-site interaction, the gapless chiral phases also disappear.Comment: 7 pages, 3 figure

    Von Neumann entropy and localization-delocalization transition of electron states in quantum small-world networks

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    The von Neumann entropy for an electron in periodic, disorder and quasiperiodic quantum small-world networks(QSWNs) are studied numerically. For the disorder QSWNs, the derivative of the spectrum averaged von Neumann entropy is maximal at a certain density of shortcut links p*, which can be as a signature of the localization delocalization transition of electron states. The transition point p* is agreement with that obtained by the level statistics method. For the quasiperiodic QSWNs, it is found that there are two regions of the potential parameter. The behaviors of electron states in different regions are similar to that of periodic and disorder QSWNs, respectively.Comment: 6 pages, 13figure

    von Neumann entropy and localization properties of two interacting particles in one-dimensional nonuniform systems

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    With the help of von Neumann entropy, we study numerically the localization properties of two interacting particles (TIP) with on-site interactions in one-dimensional disordered, quasiperiodic, and slowly varying potential systems, respectively. We find that for TIP in disordered and slowly varying potential systems, the spectrum-averaged von Neumann entropy first increases with interaction U until its peak, then decreases as U gets larger. For TIP in the Harper model[S. N. Evangelou and D. E. Katsanos, Phys. Rev. B 56, 12797(1997)], the functions of versus U are different for particles in extended and localized regimes. Our numerical results indicate that for these two-particle systems, the von Neumann entropy is a suitable quantity to characterize the localization properties of particle states. Moreover, our studies propose a consistent interpretation of the discrepancies between previous numerical results.Comment: 7 pages,13 figure

    Fidelity, fidelity susceptibility and von Neumann entropy to characterize the phase diagram of an extended Harper model

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    For an extended Harper model, the fidelity for two lowest band edge states corresponding to different model parameters, the fidelity susceptibility and the von Neumann entropy of the lowest band edge states, and the spectrum-averaged von Neumann entropy are studied numerically, respectively. The fidelity is near one when parameters are in the same phase or same phase boundary; otherwise it is close to zero. There are drastic changes in fidelity when one parameter is at phase boundaries. For fidelity susceptibility the finite scaling analysis performed, the critical exponents α\alpha, β\beta, and ν\nu depend on system sizes for the metal-metal phase transition, while not for the metal-insulator phase transition. For both phase transitions ν/α2\nu/\alpha\approx2. The von Neumann entropy is near one for the metallic phase, while small for the insulating phase. There are sharp changes in von Neumann entropy at phase boundaries. According to the variation of the fidelity, fidelity susceptibility, and von Neumann entropy with model parameters, the phase diagram, which including two metallic phases and one insulating phase separated by three critical lines with one bicritical point, can be completely characterized, respectively. These numerical results indicate that the three quantities are suited for revealing all the critical phenomena in the model.Comment: 9 pages, 12 figure