中国物理B ›› 2017, Vol. 26 ›› Issue (2): 27304-027304.doi: 10.1088/1674-1056/26/2/027304

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Enhancement of subgap conductance in a graphene superconductor junction by valley polarization

Chuan-Xin Li(李传新), Sa-Ke Wang(汪萨克), Jun Wang(汪军)   

  1. 1 College of Mathematics and Physics, Jingchu University of Technology, Jingmen 448000, China;
    2 Department of Physics, Southeast University, Nanjing 210096, China
  • 收稿日期:2016-04-28 修回日期:2016-10-31 出版日期:2017-02-05 发布日期:2017-02-05
  • 通讯作者: Jun Wang E-mail:jwang@seu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11274059 and 11074233).

Enhancement of subgap conductance in a graphene superconductor junction by valley polarization

Chuan-Xin Li(李传新)1, Sa-Ke Wang(汪萨克)2, Jun Wang(汪军)2   

  1. 1 College of Mathematics and Physics, Jingchu University of Technology, Jingmen 448000, China;
    2 Department of Physics, Southeast University, Nanjing 210096, China
  • Received:2016-04-28 Revised:2016-10-31 Online:2017-02-05 Published:2017-02-05
  • Contact: Jun Wang E-mail:jwang@seu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11274059 and 11074233).

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摘要： We theoretically study the differential conductance of a graphene/graphene superconductor junction, where the valley polarization of Dirac electrons is considered in the nonsuperconducting region. It is shown that the subgap conductance will increase monotonically with the valley-polarization strength when the chemical potential μ is near the Dirac point μ≤3Δ (Δ is the superconducting gap), whereas it will decrease monotonically when μ is far away from the Dirac point, μ≥5Δ. The former case is induced by the specular Andreev reflection while the retro-reflection accounts for the later result. Our findings may shed light on the control of conductance of a graphene superconductor junction by valley polarization.

关键词: graphene, valley polarization, subgap conductance, specular Andreev reflection

Abstract: We theoretically study the differential conductance of a graphene/graphene superconductor junction, where the valley polarization of Dirac electrons is considered in the nonsuperconducting region. It is shown that the subgap conductance will increase monotonically with the valley-polarization strength when the chemical potential μ is near the Dirac point μ≤3Δ (Δ is the superconducting gap), whereas it will decrease monotonically when μ is far away from the Dirac point, μ≥5Δ. The former case is induced by the specular Andreev reflection while the retro-reflection accounts for the later result. Our findings may shed light on the control of conductance of a graphene superconductor junction by valley polarization.

Key words: graphene, valley polarization, subgap conductance, specular Andreev reflection

中图分类号:  (Tunneling)

  • 73.40.Gk
73.23.Ad (Ballistic transport) 85.25.-j (Superconducting devices)