Andreev reflection in quantum Hall systems: 2021 state of the union

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Collage of Andreev quantum Hall systems

A combination of superconductivity with quantum Hall effect allows perfectly nonlocal crossed Andreev reflection, which has made it a target of experimental search for more than a decade.

Due to progress in material physics and emergence of new hybrid platforms, this search has resulted in a series of experiments observing a combined effect of chiral edge states and superconductivity. At the same time, measurements of Andreev conductance in the quantum Hall regime demonstrate wildly different behaviors, sometimes in disagreement with existing theoretical predictions.

In this workshop we aim to bring together experts working in the field, review observations and their interpretation, and identify the possible ways forward.

Program

Satellite talks

We welcome interested colleagues to deliver a satellite talk on closely related topics. We will announce these talks to all participants and use them in guiding the discussion. To let us know about your plan to give a talk, send us an email. Then you may either:

  • register to give a talk in the Speakers' Corner seminar series
  • share a YouTube link
  • send us a recording

We will include the satellite talks in the workshop webpage.

Schedule and recordings

Mechanisms of Andreev reflection in quantum Hall graphene

By Antonio Manesco (TU Delft)

Authors: Antonio L. R. Manesco, Ian Matthias Flór, Chun-Xiao Liu, Anton R. Akhmerov
Preprint: arXiv:2103.06722

We simulate a hybrid superconductor-graphene device in the quantum Hall regime to identify the origin of downstream resistance oscillations in a recent experiment [Zhao et. al. Nature Physics 16, (2020)]. In addition to the previously studied Mach-Zehnder interference between the valley-polarized edge states, we consider disorder-induced scattering, and the previously overlooked appearance of the counter-propagating states generated by the interface density mismatch. Comparing our results with the experiment, we conclude that the observed oscillations are induced by the interfacial disorder, and that lattice-matched superconductors are necessary to observe the alternative ballistic effects.

Organizers

Anton Akhmerov, TU Delft
Valla Fatemi, Yale University & Cornell University
Christian Schoenenberger, University of Basel

If you have any questions, you may reach us via arqh2021@virtualscienceforum.org

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