Volume 108, Number 1, October 2014
|Number of page(s)||5|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||07 October 2014|
Neutral edge modes in a superconductor–topological-insulator hybrid structure in a perpendicular magnetic field
1 Department of Physics, University of Basel - Klingelbergstrasse 82, CH-4056 Basel, Switzerland
2 School of Chemical and Physical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington - PO Box 600, Wellington 6140, New Zealand
3 Department of Physics, Harvard University - Cambridge, MA 02138, USA
Received: 16 June 2014
Accepted: 16 September 2014
We study the low-energy edge states of a superconductor–3D topological-insulator hybrid structure (NS junction) in the presence of a perpendicular magnetic field. The hybridization of electron-like and hole-like Landau levels due to Andreev reflection gives rise to chiral edge states within each Landau level. We show that by changing the chemical potential of the superconductor, this junction can be placed in a regime where the sign of the effective charge of the edge state within the zeroth Landau level changes more than once resulting in neutral edge modes with a finite value of the guiding-center coordinate. The appearance of these neutral edge modes is related to the level repulsion between the zeroth and the first Landau levels in the spectra. We also find that these neutral edge modes come in pairs, one in the zeroth Landau level and its corresponding pair in the first. Unlike ordinary neutral bogolon excitations in superconductors, the neutral modes found by us have a finite speed and, thus, the potential to carry a heat current.
PACS: 73.20.At – Surface states, band structure, electron density of states / 73.25.+i – Surface conductivity and carrier phenomena / 74.45.+c – Proximity effects; Andreev reflection; SN and SNS junctions
© EPLA, 2014
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