Disorder-enabled Andreev reflection of a quantum Hall edge

Area of Science:

• Condensed matter physics
• Quantum phenomena
• Mesoscopic physics

Background:

• Quantum Hall effect describes electron behavior in 2D systems under strong magnetic fields.
• Superconductors exhibit zero electrical resistance below a critical temperature.
• Proximity effect describes the influence of a superconductor on an adjacent non-superconducting material.

Purpose of the Study:

• To develop a theoretical framework for charge transport along quantum Hall edges proximitized by superconductors.
• To investigate the role of disorder in Andreev reflection at the proximitized edge.
• To explain the observed stochastic conductance fluctuations in recent experiments.

Main Methods:

• Theoretical modeling of charge transport.
• Analysis of Andreev reflection in disordered superconducting environments.
• Statistical analysis of conductance fluctuations.

Main Results:

• Andreev reflection is generically suppressed in translationally invariant systems.
• Disorder in the superconductor enables random Andreev reflection.
• Proximitized quantum Hall edges exhibit stochastic conductance with giant sign-alternating fluctuations and zero average.
• The statistical distribution of conductance and its dependencies on electron density, magnetic field, and temperature were determined.

Conclusions:

• The developed theory explains the experimental observations of stochastic conductance in proximitized quantum Hall edge states.
• Disorder-induced random Andreev reflection is crucial for understanding the observed phenomena.
• The findings provide insights into the interplay between quantum Hall physics and superconductivity.