Spontaneous formation of pi-soliton in a superconducting wire with an odd number of electrons

Abstract
We consider a one-dimensional superconducting wire where the total number of electrons can be controlled in the Coulomb blockade regime. We predict that a pi-soliton (kink) will spontaneously form in the system when the number of electron is odd, because this configuration has a lower energy. If the wire with an odd number of electrons is closed in a ring, the phase difference on 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  qbit. The paper is available at: http://publish.aps.org/abstract/PRL/v89/p17002 Phys. Rev. Lett. 89, 017002 (2002) H.-J. Kwon and V.M. Yakovenko "Spontaneous formation of a pi Soliton in a Number of Electrons"