Condensed Matter Physics Seminar

2 p.m., Thursday, February 27, 2003
Room 1201, Physics Building

 Andreev bound states in superconductors: Spontaneous soliton formation and fractional Josephson effect

Victor Yakovenko

(University of Maryland)

Abstract:  First [1], we demonstrate that a pi-soliton (kink) should spontaneously form in a 1D superconducting wire when the total number of electron is odd, because Andreev bound states in the soliton would decrease the total energy of the system. If such a wire is closed in a ring, the phase difference between the two sides of the soliton will generate a supercurrent detectable by SQUID. The two degenerate states with the current flowing clockwise or counterclockwise can be utilized as a qubit. Second [2], we show that the contribution of the Andreev bound states to the Josephson effect between two Q1D px-wave or two Q2D d-wave superconductors has the period of 4p in the phase difference. Consequently, the ac Josephson current has the fractional frequency eV/h, a half of the conventional value. In the tunneling limit, the Josephson current is proportional to the first power of tunneling amplitude, thus the critical current is greatly enhanced and has an unusual temperature dependence.

[1] H.-J. Kwon and V. M. Yakovenko, Phys. Rev. Lett. 89, 017002 (2002).
[2] H.-J. Kwon, K. Sengupta, and V. M. Yakovenko, cond-mat/0210148.

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