Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 17: Transport: Topological insulators 1 (TT with DS/HL)
HL 17.8: Talk
Monday, March 16, 2015, 17:15–17:30, A 053
Manipulation of helical edge state transport by a quantum magnet — •Peter Silvestrov1, Patrik Recher1, and Piet Brouwer2 — 1Institute for Mathematical Physics, TU Braunschweig — 2Dahlem Center for Complex Quantum Systems, FU Berlin
Application of a magnetic field is usually considered as a way to open the gap in the spectrum of helical edge states, leading to a blocking of the edge current. Nevertheless, it was shown recently that the current is fully transmitted through the gapped region in case of interaction with a quantum magnet[1]. Here we consider other interesting features of the helical edge state current interacting with the magnet. First, we notice that although the current is transmitted, all electrons with energies close to the Fermi energy are fully reflected. The actual current is carried by the electrons with energies below the gap and well below the Fermi energy. This suggests that the magnet while allowing passing the current, fully blocks the thermal transport thereby acting as a cooler for the injected electron beam. Our second setup consists of two helical edges covered by the same magnet. The current injected into one edge creates a non-equilibrium magnetization driving a current in the second edge. The current in the first edge is now half-reflected and half-transmitted by the magnet. However, the partial reflection of the current does not cause any shot noise.
[1] Q.Meng, S.Vishveshwara, T.L.Hughes, arXiv:1312.7303.