[qmeso-seminar] семинар сектора 2 марта

[Mikhail A. Skvortsov]

                     СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

                          пятница 2 марта, 15:00, ИТФ

                Elio König (Karlsruhe Institute of Technology)

           Metal-insulator transition in 2D random fermion systems 
                          of chiral symmetry classes

Field-theoretical approach to Anderson localization in 2D disordered
fermionic systems of chiral symmetry classes (BDI, AIII, CII) is developed.
Important representatives of these symmetry classes are random hopping
models on bipartite lattices at the band center. As was found by Gade and
Wegner two decades ago within the sigma-model formalism, quantum
interference effects in these classes are absent to all orders of
perturbation theory. We demonstrate that the quantum localization effects
emerge when the theory is treated non-perturbatively. Specifically, they
are controlled by topological vortex-like excitations of the sigma models.
We derive renormalization group equations including these non-perturbative
contributions. Analyzing them, we find that the 2D disordered systems of
chiral classes undergo a metal-insulator transition driven by topologically
induced Anderson localization. We also show that the Wess-Zumino and Z_2
theta terms on surfaces of 3D topological insulators (in classes AIII and 
CII, respectively) overpower the vortex-induced localization.

по работе E.J. König, P. M. Ostrovsky, I. V. Protopopov, A. D. Mirlin,
"Metal-insulator transition in 2D random fermion systems of chiral symmetry
classes", arXiv:1201.6288v1