As Contributors: | Götz Uhrig · Maik Malki |

Arxiv Link: | http://arxiv.org/abs/1709.04224v1 |

Date submitted: | 2017-09-14 |

Submitted by: | Uhrig, Götz |

Submitted to: | SciPost Physics |

Domain(s): | Theoretical |

Subject area: | Condensed Matter Physics - Theory |

Topological aspects represent currently a boosting area in condensed matter physics. Yet there are very few suggestions for technical applications of topological phenomena. Still, the most important is the calibration of resistance standards by means of the integer quantum Hall effect. We propose modifications of samples displaying the integer quantum Hall effect which render the tunability of the Fermi velocity possible by external control parameters such as gate voltages. In this way, so far unexplored possibilities arise to realize devices such as tunable delay lines and interferometers.

Editor-in-charge assigned, manuscript under review

The paper is very well organized and contains specific details of the calculations.

See "requested changes"

This manuscript provides details of tunable delay lines which work in the integer quantum Hall regime. I find this effort highly original and important as there are relatively few experimental realizations of devices which rely on the so called topological property or the presence of the edge states.

I found only one issue which needs clarification. Past page 15, the authors discuss edge states coupled to a series of bays. The authors have explained clearly that the Fermi velocity will be slowed down substantially in the region where the edge couples to one bay. However, in between such coupled regions there are other regions, each of length L_xp-L_o which I believe are not coupled to the bays, therefore the Fermi velocity is unchanged here. I therefore suspect that in Fig.11-14 the average velocity is plotted. As such, such an average velocity will indeed describe the proposed delay line.

However, from the text of the manuscript, is was not clear if the authors did indeed compute such an average speed. Should the average speed decrease all the way to zero at certain gate voltages in Fig.14?

So I am asking the authors to clarify if in Fig.11-14 they intended to discuss the average velocity.

- validity: top
- significance: top
- originality: top
- clarity: high
- formatting: excellent
- grammar: perfect