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Andreev Reflection in the Quantum Hall Regime at an Al/InAs Junction on a Cleaved Edge
Takafumi Akiho1, Hiroshi Irie1, Yusuke Nakazawa1
1NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan.
Nano Letters
|November 6, 2024
Summary
We created a novel superconductor/semiconductor junction enabling superconductivity and quantum Hall effects to coexist. This breakthrough offers new insights into their complex interplay in advanced electronic materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Superconductor/semiconductor junctions are crucial for exploring exotic quantum phenomena.
- Achieving coexistence of superconductivity and quantum Hall (QH) effects requires specific material properties and experimental conditions.
Purpose of the Study:
- To fabricate and characterize a novel superconductor/semiconductor junction for studying the interplay between superconductivity and QH effects.
- To investigate Andreev reflection and superconducting gap opening in a unique material geometry.
Main Methods:
- Fabrication of an aluminum (Al)/indium arsenide (InAs) junction using cleaved edge overgrowth.
- Utilizing a thin Al/Pt/Al trilayer on an in situ cleaved InAs quantum well heterostructure.
- Employing Andreev reflection and bias spectroscopy measurements.
Main Results:
- Achieved a superconducting critical field of ~5 Tesla, enabling superconductivity and QH effects coexistence down to filling factor ν = 3.
- Demonstrated a virtually barrier-free junction with conductance enhancement limited by Fermi velocity mismatch.
- Observed opening of a superconducting gap in the QH regime, with reduced downstream resistance indicating electron-hole Andreev conversion.
Conclusions:
- The developed junction provides a new experimental platform for studying superconductivity and QH effects.
- The results highlight the potential for clean edge-contacted junctions with superconducting electrodes narrower than the coherence length.
- Opens new avenues for theoretical and experimental research at the intersection of superconductivity and quantum phenomena.
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