[qmeso-seminar] семинар сектора 4 апреля

[Mikhail A. Skvortsov]

                     СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

                          пятница 4 апреля, 15:00, ИТФ


                                 Dmitry Bagrets
           (Institute for Theoretical Physics, University of Cologne)

       Quantum criticality in quasi one-dimensional topological nanowires


Using the combination of analytical and numerical techniques we develop the
theory of quantum criticality in disordered topological multi-channel nanowires
of symmetry classes AIII and BDI [1]. The minimal representative phase portrait
is characterized by two parameters $(\mu, w)$, where $\mu$ is the external
control parameter (e.g. the chemical potential) and $w$ is the disorder
strength. With the increase of $w$ at a fixed value of $\mu$ the wires
generically undergo a sequence of topological phase transitions before the
asymptotic state of a trivial Anderson insulator is reached. The universal
description of the systems is given in terms of two parameters $(g,\chi)$, 
where $g$ is conductance and $\chi$ is a topological angle. Contour lines of
half-integer valued $\chi$ in $(\mu, w)$-parameter space define phase boundaries
between distinct topological sectors. Upon increasing the length of the wire,
the pair $(g, \chi)$ exhibits flow similar to the celebrated two parameter flow
describing the class A quantum Hall insulator. However, unlike the quantum Hall
system, an exact analytical description of the entire phase diagram can be
given. We corroborate the quantitative validity of our theory by comparison to
numerical transfer matrix computations.

[1] A. Altland, D. Bagrets, L. Fritz, A. Kamenev, H. Schmiedt, arXiv:1402.1738