中国物理B ›› 2007, Vol. 16 ›› Issue (5): 1450-1458.doi: 10.1088/1009-1963/16/5/047

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

Ground state of a superconducting π ring array under external magnetic fields

冯运1, 王福仁2, 戴远东2, 李壮志3   

  1. (1)College of Mechanical and Electronic Engineering, Hebei University of Science\\ and Technology, Shijiazhuang {\rm 050054, China; (2)Mesoscopic Physics National Laboratory and Department of Physics,Peking University, Beijing 100871, China; (3)Mesoscopic Physics National Laboratory and Department of Physics,Peking University, Beijing 100871, China;College of Physical Science and Information Engineering,Hebei Normal University, Shijiazhuang 050016, China
  • 收稿日期:2006-09-25 修回日期:2006-12-04 出版日期:2007-05-20 发布日期:2007-05-20
  • 基金资助:
    Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB601007).

Ground state of a superconducting π ring array under external magnetic fields

Li Zhuang-Zhi(李壮志)a)b)†, Feng Yun(冯运)c), Wang Fu-Ren(王福仁)a), and Dai Yuan-Dong(戴远东)a)   

  1. a Mesoscopic Physics National Laboratory and Department of Physics, Peking University, Beijing 100871, China; b College of Physical Science and Information Engineering,Hebei Normal University, Shijiazhuang 050016, China; c College of Mechanical and Electronic Engineering, Hebei University of Science and Technology, Shijiazhuang 050054, China
  • Received:2006-09-25 Revised:2006-12-04 Online:2007-05-20 Published:2007-05-20
  • Supported by:
    Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB601007).

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摘要： The ground state of a two-dimensional square superconducting π ring array has been investigated. The circulating currents of the π ring array will spontaneously magnetize to the `antiferromagnetic' arrangement with directions of the nearest-neighbouring currents circulating oppositely in the absence of an external magnetic field. It is found that the external magnetic field could destroy the anti-parallel configuration effectively. The external magnetic field needed to destroy the anti-parallel configuration is related to the superconducting \pi ring's inductance parameter β=2\pi L Ic/\phi0. For a small β the anti-parallel configuration, which is the lowest-energy ground state of the system, will be fully destroyed and changed to the configuration that the circulating currents have the same direction and parallel to the external magnetic field when the magnetic flux reaches \phi0/4 in each ring. Moreover, the magnetic field needed to destroy the anti-parallel configuration will be very small when β is large enough.

Abstract: The ground state of a two-dimensional square superconducting $\pi$ ring array has been investigated. The circulating currents of the $\pi$ ring array will spontaneously magnetize to the `antiferromagnetic' arrangement with directions of the nearest-neighbouring currents circulating oppositely in the absence of an external magnetic field. It is found that the external magnetic field could destroy the anti-parallel configuration effectively. The external magnetic field needed to destroy the anti-parallel configuration is related to the superconducting $\pi$ ring's inductance parameter $\beta=2\pi LI_{\rm c}/\phi_0$. For a small $\beta$ the anti-parallel configuration, which is the lowest-energy ground state of the system, will be fully destroyed and changed to the configuration that the circulating currents have the same direction and parallel to the external magnetic field when the magnetic flux reaches $\phi_0/4$ in each ring. Moreover, the magnetic field needed to destroy the anti-parallel configuration will be very small when $\beta$ is large enough.

Key words: $\pi$ ring array, Josephson junction, spontaneous magnetization

中图分类号:  (Magnetic properties including vortex structures and related phenomena)

  • 74.25.Ha
74.25.Bt (Thermodynamic properties) 74.25.Sv (Critical currents)