Baselmans J J A, Heikkilä T T, van Wees B J, Klapwijk T M
Department of Applied Physics and Materials Science Center, University of Groningen, Nijenborg 4, 9747 AG Groningen, The Netherlands.
Phys Rev Lett. 2002 Nov 11;89(20):207002. doi: 10.1103/PhysRevLett.89.207002. Epub 2002 Oct 29.
We measure the full supercurrent-phase relation of a controllable pi junction around the transition from the conventional 0 state to the pi state. We show that around the transition the Josephson supercurrent-phase relation changes from I(sc) approximately I(c)sin((phi) to I(sc) approximately I(c)sin((2phi). This implies that, around the transition, two minima in the junction free energy exist, one at phi=0 and one at phi=pi, whereas only one minimum exists at the 0 state (at phi=0) and at the pi state (at phi=pi). Theoretical calculations based on the quasiclassical theory are in good agreement with the observed behavior.
我们测量了一个可控π结从传统的0态到π态转变过程中的完整超流-相位关系。我们表明，在转变附近，约瑟夫森超流-相位关系从I(sc)≈I(c)sin(φ)变为I(sc)≈I(c)sin(2φ)。这意味着，在转变附近，结自由能存在两个最小值，一个在φ = 0处，一个在φ = π处，而在0态（φ = 0）和π态（φ = π）时仅存在一个最小值。基于准经典理论的理论计算与观测行为吻合良好。
