| Authors: |
S. Nishino
and K. Yakubo
|
| Editors: |
Luciano Pietronero
and Vittorio Loreto
and Stefano Zapperi
|
| URL: |
http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=372 |
| Tags: |
anderson
band
class
flat
interaction
localization
spin-orbit
statphys23
topic-8
transition
universality
|
| Abstract: |
We find a disorder-induced insulator-metal-insulator reentrant transition
in a novel two-dimensional noninteracting electron system which has
highly-degenerated eigenstates unless
introducing disorders.
First, we propose a tight-binding Hamiltonian on a square lattice
decorated in a specific manner with spin-orbit interactions described by
the Ando model.
We show that the system has a dispersionless band, which is called flat
band, at zero energy in its band structure.
Next, we introduce disorders into on-site potentials of the Hamiltonian.
Due to the diagonal disorder, the flat band becomes a finite width
single band.
Since the system belongs to the symplectic universality class because of
spin-orbit interactions breaking the spin-rotational symmetry, the
metal-insulator transition can be expected in this band.
In order to examine the transition in this system, we employed the
nearest-neighbor level spacing statistics which is a powerful tool for studying
the Anderson transition.
We numerically diagonalize the Hamiltonian and calculate the
distribution function of nearest-neighbor level spacings $P(s)$ which
becomes the Wigner and the Poissonian distributions for metallic and
insulating states, respectively.
For a fixed nonzero energy, $P(s)$ is found to be close to the
Poissonian distribution for weak and very strong disorders, while
$P(s)$ becomes the Wigner surmise for intermediate disorders.
This behavior of $P(s)$ implies the existence of the
insulator-metal-insulator reentrant transition as increasing the strength of
disorder.
We carry out the finite-size scaling analysis of the level statistics to
determine the precise position of the transition.
It is found that the insulator-metal-insulator transition exists over a
wide energy region in our two-dimensional disordered systems. |
@incollection{statphys23_0372,
title = {Insulator-Metal-Insulator Transition in Two Dimensional Disordered Electronic Systems with Flat Bands},
address = {Genova, Italy},
author = {S. Nishino and K. Yakubo},
booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics},
editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi},
month = {9-13 July},
url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=372},
year = {2007},
abstract = {We find a disorder-induced insulator-metal-insulator reentrant transition
in a novel two-dimensional noninteracting electron system which has
highly-degenerated eigenstates unless
introducing disorders.
First, we propose a tight-binding Hamiltonian on a square lattice
decorated in a specific manner with spin-orbit interactions described by
the Ando model.
We show that the system has a dispersionless band, which is called flat
band, at zero energy in its band structure.
Next, we introduce disorders into on-site potentials of the Hamiltonian.
Due to the diagonal disorder, the flat band becomes a finite width
single band.
Since the system belongs to the symplectic universality class because of
spin-orbit interactions breaking the spin-rotational symmetry, the
metal-insulator transition can be expected in this band.
In order to examine the transition in this system, we employed the
nearest-neighbor level spacing statistics which is a powerful tool for studying
the Anderson transition.
We numerically diagonalize the Hamiltonian and calculate the
distribution function of nearest-neighbor level spacings $P(s)$ which
becomes the Wigner and the Poissonian distributions for metallic and
insulating states, respectively.
For a fixed nonzero energy, $P(s)$ is found to be close to the
Poissonian distribution for weak and very strong disorders, while
$P(s)$ becomes the Wigner surmise for intermediate disorders.
This behavior of $P(s)$ implies the existence of the
insulator-metal-insulator reentrant transition as increasing the strength of
disorder.
We carry out the finite-size scaling analysis of the level statistics to
determine the precise position of the transition.
It is found that the insulator-metal-insulator transition exists over a
wide energy region in our two-dimensional disordered systems.},
keywords = {anderson band class flat interaction localization spin-orbit statphys23 topic-8 transition universality }
}
::