Andreev reflection of quantum Hall states through a quantum point contact

• Published in: Physical review. B 2024-01, Vol.109 (3), Article 035430
• Main Authors: Hatefipour, Mehdi, Cuozzo, Joseph J., Levy, Ido, Strickland, William M., Langone, Dylan, Rossi, Enrico, Shabani, Javad
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.109.035430

Here, we investigate the interplay between the quantum Hall (QH) effect and superconductivity in InAs surface quantum well (SQW)/NbTiN heterostructures using a quantum point contact (QPC). We use QPC to control the proximity of the edge states to the superconductor. By measuring the upstream and downstream resistances of the device, we investigate the efficiency of Andreev conversion at the InAs/NbTiN interface. Our experimental data is analyzed using the Landauer Büttiker formalism, generalized to allow for Andreev reflection processes. We show that by varying the voltage of the QPC, VQPC, the average Andreev reflection, A, at the QH-SC interface can be tuned from 50% to ~ 10%. The evolution of A with VQPC extracted from the measurements exhibits plateaus separated by regions for which A varies continuously with VQPC. The presence of plateaus suggests that for some ranges of VQPC the QPC might be pinching off almost completely from the QH-SC interface some of the edge modes. Our work shows a new experimental setup to control and advance the understanding of the complex interplay between superconductivity and QH effect in two-dimensional gas systems.