Robust integer and fractional helical modes in the quantum Hall effect

• Published in: Nature physics Vol. 14; no. 4; pp. 411 - 416
• Main Authors: Ronen, Yuval, Cohen, Yonatan, Banitt, Daniel, Heiblum, Moty, Umansky, Vladimir
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2018; Nature Publishing Group
• Subjects: 142/126; 639/766/119/1000; 639/766/119/1001; 639/766/119/2792; 639/766/119/2794; Atomic; Banded structure; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Electromagnetism; Electronic systems; Gallium arsenide; Hall effect; Interferometers; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Quantum computing; Quantum Hall effect; Quantum wells; Superconductivity; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-017-0035-2

Electronic systems harboring one-dimensional helical modes, where spin and momentum are locked, have lately become an important field of their own. When coupled to a conventional superconductor, such systems are expected to manifest topological superconductivity; a unique phase hosting exotic Majorana zero modes. Even more interesting are fractional helical modes, yet to be observed, which open the route for realizing generalized parafermions. Possessing non-Abelian exchange statistics, these quasiparticles may serve as building blocks in topological quantum computing. Here, we present a new approach to form protected one-dimensional helical edge modes in the quantum Hall regime. The novel platform is based on a carefully designed double-quantum-well structure in a GaAs-based system hosting two electronic sub-bands; each tuned to the quantum Hall effect regime. By electrostatic gating of different areas of the structure, counter-propagating integer, as well as fractional, edge modes with opposite spins are formed. We demonstrate that, due to spin protection, these helical modes remain ballistic over large distances. In addition to the formation of helical modes, this platform can serve as a rich playground for artificial induction of compounded fractional edge modes, and for construction of edge-mode-based interferometers. Helical modes are induced in a high-mobility two-dimensional electron gas without strong spin–orbit coupling. This platform provides a versatile playground for investigating compounded quantum Hall edge states.