超导约瑟夫森链的Y结
Y-junction of superconducting Josephson chains
摘要：
我们表明，对于相关的制造和控制参数的值，一个有吸引力的有限耦合不动点出现在超导约瑟夫森链的Y-结的相图。新的不动点仅在穿过网络中心回路的无量纲通量$f$等于$π$时出现，因此不会破坏时间反演不变性;对于$f \neq π$，只有强耦合不动点作为稳定的吸引不动点存在。相位滑移（瞬子）有一个至关重要的作用，在建立这种过渡：我们确实表明，在$f = π$，一组新的瞬子-W-瞬子-发挥作用，以破坏强耦合不动点。最后，我们提供了一个详细的帐户约瑟夫森电流相位关系沿武器的网络，附近的每一个允许的固定点。我们的研究结果表明，超导约瑟夫森链的Y-结的相图之间的显着的相似之处，发现在分析的量子布朗运动挫折平面晶格。
英文摘要：
We show that, for pertinent values of the fabrication and control parameters, an attractive finite coupling fixed point emerges in the phase diagram of a Y-junction of superconducting Josephson chains. The new fixed point arises only when the dimensionless flux $f$ piercing the central loop of the network equals $π$ and, thus, does not break time-reversal invariance; for $f \neq π$, only the strongly coupled fixed point survives as a stable attractive fixed point. Phase slips (instantons) have a crucial role in establishing this transition: we show indeed that, at $f = π$, a new set of instantons -the W-instantons- comes into play to destabilize the strongly coupled fixed point. Finally, we provide a detailed account of the Josephson current-phase relationship along the arms of the network, near each one of the allowed fixed points. Our results evidence remarkable similarities between the phase diagram accessible to a Y-junction of superconducting Josephson chains and the one found in the analysis of quantum Brownian motion on frustrated planar lattices.
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