1202.2108 (Bryan Leung et al.)

Effect of Strong Disorder in a 3-Dimensional Topological Insulator:
Phase Diagram and Maps of the Z2 Invariant    [PDF]

Bryan Leung, Emil Prodan

We study the effect of strong disorder in a 3-dimensional topological
insulators with time-reversal symmetry and broken inversion symmetry. Firstly,
using level statistics analysis, we demonstrate the persistence of delocalized
bulk states even at large disorder. The delocalized spectrum is seen to display
the levitation and pair annihilation effect, indicating that the delocalized
states continue to carry the Z2 invariant after the onset of disorder.
Secondly, the Z2 invariant is computed via twisted boundary conditions using a
novel and efficient numerical algorithm. We demonstrate that the Z2 invariant
remains quantized and non-fluctuating even after the spectral gap becomes
filled with dense localized states. In fact, our results indicate that the Z2
invariant remains quantized until the mobility gap closes or until the Fermi
level touches the mobility edges. Based on such data, we compute the phase
diagram of the Bi2Se3 topological material as function of disorder strength and
position of the Fermi level.

View original: http://arxiv.org/abs/1202.2108