Detection of Majorana Kramers Pairs Using a Quantum Point Contact.

Area of Science:

• Condensed Matter Physics
• Quantum Information Science
• Materials Science

Background:

• Quantum spin Hall (QSH) effect enables dissipationless edge states.
• Majorana zero-energy bound states (MZBS) are exotic quasiparticles with potential in topological quantum computing.
• Josephson junctions and quantum point contacts (QPCs) are key components in quantum electronic devices.

Purpose of the Study:

• To propose and investigate a novel experimental setup for detecting Kramers pairs of MZBS.
• To explore the signatures of MZBS in transport measurements using an integrated QPC.
• To establish a robust and experimentally feasible method for Majorana detection.

Main Methods:

• Integration of a QPC and a Josephson junction on a QSH insulator (InAs/GaSb quantum wells).
• Theoretical investigation of electron scattering properties at the QPC in the presence of MZBS.
• Analysis of differential conductances and current cross-correlations under varying magnetic fields.

Main Results:

• The proposed setup hosts Kramers pairs of MZBS when superconducting phases differ by π.
• A robust switching from normal to Andreev scattering at the QPC edges is observed due to MZBS.
• Multiterminal differential conductances exhibit sign-oscillations with magnetic field tuning, serving as a qualitative signature.
• This signature is also present in current cross-correlations, unaffected by quantitative measurement challenges.

Conclusions:

• The integrated QPC-Josephson junction system provides a reliable platform for detecting MZBS.
• The observed switching in scattering nature and oscillating conductances offer a significant advantage over quantitative Majorana signatures.
• This work paves the way for experimental verification of MZBS and their application in topological quantum computing.