Crossed Andreev reflection in spin-polarized chiral edge states due to the Meissner effect

TL;DR

This paper investigates how the Meissner effect induces nonlocal crossed Andreev reflection in a quantum Hall-superconductor system, leading to a gap in edge states and potential Majorana states, with implications for quantum transport.

Contribution

It demonstrates that the Meissner effect can enable crossed Andreev reflection in spin-polarized edge states without spin-orbit coupling or magnetic textures.

Findings

Negative resistance due to nonlocal Andreev processes

Peaks in zero-energy local density of states stable to disorder

Potential emergence of Majorana bound states

Abstract

We consider a hybrid quantum Hall-superconductor system, where a superconducting finger with oblique profile is wedged into a two-dimensional electron gas in the presence of a perpendicular magnetic field, as considered by Lee et al., Nat. Phys. 13, 693 (2017). The electron gas is in the quantum Hall regime at filling factor $\nu=1$. Due to the Meissner effect, the perpendicular magnetic field close to the quantum Hall-superconductor boundary is distorted and gives rise to an in-plane component of the magnetic field. This component enables nonlocal crossed Andreev reflection between the spin-polarized chiral edge states running on opposite sides of the superconducting finger, thus opening a gap in the spectrum of the edge states without the need of spin-orbit interaction or nontrivial magnetic textures. We compute numerically the transport properties of this setup and show that a negative resistance exists as a consequence of nonlocal Andreev processes. We also obtain numerically the zero-energy local density of states, which systematically shows peaks stable to disorder. The latter result is compatible with the emergence of Majorana bound states.