Enhanced topological superconductivity in an asymmetrical planar Josephson junction

doi:10.1088/1674-1056/acaa29

中国物理B ›› 2023, Vol. 32 ›› Issue (4): 40307-040307.doi: 10.1088/1674-1056/acaa29

Enhanced topological superconductivity in an asymmetrical planar Josephson junction

Erhu Zhang(张二虎) and Yu Zhang(张钰)^†

Department of Applied Physics, School of Science, Xi'an Jiaotong University, Xi'an 710049, China

收稿日期:2022-08-08 修回日期:2022-12-04 接受日期:2022-12-09 出版日期:2023-03-10 发布日期:2023-03-23
通讯作者: Yu Zhang E-mail:646907259@qq.com
基金资助:
Project supported by the National Natural Science Foundation of China (Grant No. 11974271).

Enhanced topological superconductivity in an asymmetrical planar Josephson junction

Erhu Zhang(张二虎) and Yu Zhang(张钰)^†

Department of Applied Physics, School of Science, Xi'an Jiaotong University, Xi'an 710049, China

Received:2022-08-08 Revised:2022-12-04 Accepted:2022-12-09 Online:2023-03-10 Published:2023-03-23
Contact: Yu Zhang E-mail:646907259@qq.com
Supported by:
Project supported by the National Natural Science Foundation of China (Grant No. 11974271).

摘要/Abstract

摘要： As a platform for holding Majorana zero models (MZMs), the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges. One is a combination of mirror and time-reversal symmetries may make the system hold multiple pairs of MZMs. The other is that a soft gap dominated by a large momentum occurs in a clean system. To solve these problems, asymmetric junction can be introduced. Breaking this symmetry changes the symmetry class from class BDI to class D, and only a single pair of MZMs can be left at the boundary of the system. We numerically study four cases that create an asymmetric system and find out different superconducting pairing potential, different coupling coefficients between two-dimensional electron gases (2DEGs) and two superconducting bulks, different widths of two superconducting bulks make the gap of the system decrease at the optimal value, but make the gap at the minimum value increases. And the zigzag-shape quasi-one-dimensional junction eliminates the large momentum parallel to the junction and enhances the gap at the large momentum. However, the zigzag-shape junction cannot increase the gap at the region of multiple pairs of MZMs in a symmetric system. We show that by combining zigzag-shape junction with different coupling coefficients, the system can maintain a large gap (≈0.2 Δ) in a wide region of the parameter space.

关键词: topological superconductivity, planar Josephson junction, Majorana zero modes

Abstract: As a platform for holding Majorana zero models (MZMs), the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges. One is a combination of mirror and time-reversal symmetries may make the system hold multiple pairs of MZMs. The other is that a soft gap dominated by a large momentum occurs in a clean system. To solve these problems, asymmetric junction can be introduced. Breaking this symmetry changes the symmetry class from class BDI to class D, and only a single pair of MZMs can be left at the boundary of the system. We numerically study four cases that create an asymmetric system and find out different superconducting pairing potential, different coupling coefficients between two-dimensional electron gases (2DEGs) and two superconducting bulks, different widths of two superconducting bulks make the gap of the system decrease at the optimal value, but make the gap at the minimum value increases. And the zigzag-shape quasi-one-dimensional junction eliminates the large momentum parallel to the junction and enhances the gap at the large momentum. However, the zigzag-shape junction cannot increase the gap at the region of multiple pairs of MZMs in a symmetric system. We show that by combining zigzag-shape junction with different coupling coefficients, the system can maintain a large gap (≈0.2 Δ) in a wide region of the parameter space.

Key words: topological superconductivity, planar Josephson junction, Majorana zero modes

中图分类号: (Quantum computation architectures and implementations)

03.67.Lx

74.78.-w (Superconducting films and low-dimensional structures) 74.45.+c (Proximity effects; Andreev reflection; SN and SNS junctions)

Erhu Zhang(张二虎) and Yu Zhang(张钰). Enhanced topological superconductivity in an asymmetrical planar Josephson junction[J]. 中国物理B, 2023, 32(4): 40307-040307.

Erhu Zhang(张二虎) and Yu Zhang(张钰). Enhanced topological superconductivity in an asymmetrical planar Josephson junction[J]. Chin. Phys. B, 2023, 32(4): 40307-040307.

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Enhanced topological superconductivity in an asymmetrical planar Josephson junction

Enhanced topological superconductivity in an asymmetrical planar Josephson junction

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