VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Thursday 8
Topological Insulators

› 9:30 - 10:00 (30min)
Topological insulators, helical electrons, and Rashba interactions
Henrik Johannesson  1@  
1 : University of Gothenburg  -  Website
Department of Physics, Fysikgården 1, SE 412 96 Gothenburg -  Sweden

Topological insulators are new states of quantum matter characterized by an insulating gap in the bulk and gapless edge or surface states. These states - which give rise to the quantum spin Hall effect in two dimensions - are robust against time-reversal invariant perturbations when the electron-electron (e-e) interaction is strongly screened. However, for weak screening this property is lost. As a case in point I will discuss the effect of a Rashba spin-orbit interaction on the helical edge states of a quantum spin Hall insulator. A Rashba coupling which is randomly fluctuating in space - due to dopant ions at the quantum well interface - is found to open a scattering channel which causes localization of the edge modes. A periodic modulation of the Rashba coupling, produced by a periodic gating of the heterostructure, makes the edge insulating already at intermediate strengths of the e-e interaction [1]. Other surprising effects from the interplay between e-e and Rashba interactions is the suppression of the Kondo effect at the edge of a quantum spin Hall insulator [2], and the emergence of a "synthetic" helical electron liquid in a quantum wire subject to a spatially modulated Rashba coupling [3].

[1] A. Ström, H. Johannesson, G. I. Japaridze, Phys. Rev. Lett. 104, 256804 (2010).[2] E. Eriksson, A. Ström, G. Sharma, H. Johannesson, Phys. Rev. B 86, 161103(R) (2012).[3] G. I. Japaridze, H. Johannesson, M. Malard, to appear.

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