37 research outputs found
Mode entanglement of an electron in one-dimensional determined and random potentials
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
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 chain in a transverse field (TF)
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 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 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
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
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
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 , ,
and depend on system sizes for the metal-metal phase transition, while
not for the metal-insulator phase transition. For both phase transitions
. 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