Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 103: Transport: Poster Session
TT 103.45: Poster
Donnerstag, 19. März 2015, 15:00–18:00, Poster B
Transport at the edge of a 2D topological insulator — •Eslam Khalaf and Pavel Ostrovsky — Max Planck institute for solid state research, Stuttgart, Germany
We consider transport characteristics of the 2D topological insulator edge states in the presence of disorder. Two general setups are studied: a junction of the two quantum-Hall insulators and a relatively thick HgTe quantum well. In the first setup, an imbalance between the number of left- and right propagating modes (nL and nR) may occur at the interface if the filling factor is different on both sides of the junction. In this case, |nL − nR| edge modes are topologically protected while all other states get eventually localized by disorder. If an edge of a thick HgTe quantum well carries an odd number of modes, one of them is also topologically protected from localization while others are localized at sufficiently long scales. For both systems, we compute the distribution of transmission probabilities and mesoscopic conductance fluctuations. Technically, this requires solving the one-dimensional non-linear sigma model with a topological term and source terms. The transfer-matrix formalism is employed which maps the problem to the problem of finding the eigenfunctions of Laplace operator on a symmetric superspace. For the quantum-Hall edge, the main effect of topology is the development of a gap in the transmission probability distribution around unit transmission for all length scales. In the case of HgTe quantum well, the probability distribution is also suppressed close to unit transmission but does not exhibit a hard gap.