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Gate-Tunable Ambipolar Josephson Current in a Topological Insulator.
Bomin Zhang1, Xiaoda Liu1, Junjie Qi2
1Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Nano Letters
|December 3, 2025
Summary
We demonstrate gate-tunable Josephson current in topological insulator devices, crucial for Majorana physics. This tunable transport paves the way for exploring electrically controlled Majorana modes.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Physics
Background:
- Topological insulators (TI) with proximity-induced superconductivity are key platforms for Majorana physics.
- Dirac surface states in TIs offer unique electronic properties.
Purpose of the Study:
- To demonstrate gate-tunable ambipolar Josephson current in topological insulator-based Josephson junctions.
- To investigate the influence of chemical potential and film thickness on Josephson transport.
- To lay the foundation for electrically tunable Majorana modes.
Main Methods:
- Fabrication of lateral Josephson junction (JJ) devices using bulk-insulating (Bi,Sb)2Te3 thin films grown by molecular beam epitaxy (MBE).
- Electrical transport measurements to probe gate-tunable ambipolar Josephson current.
- Numerical simulations to understand the observed transport phenomena.
Main Results:
- Pronounced gate-tunable ambipolar Josephson current observed in thinner films, suppressed near the Dirac point but persisting across it.
- Weaker ambipolar response in thicker films, attributed to the coexistence of surface and bulk conduction.
- Supercurrent resilience to magnetic fields decreases near the Dirac point.
Conclusions:
- Gate-tunable ambipolar Josephson transport demonstrated in topological insulator devices.
- Understanding of surface and bulk conduction interplay in superconductivity is enhanced.
- Provides a pathway for realizing electrically tunable Majorana modes for quantum computing applications.
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