Current-induced SQUID behavior of superconducting Nb nano-rings
Current-induced SQUID behavior of superconducting Nb nano-rings
复制标题
超导铌纳米环的电流诱导SQUID行为
作者：
O. Sharon;A. Shaulov;J. Berger;A. Sharoni;Y. Yeshurun
超导环的临界温度随穿过环的磁通量周期性变化，从而引起著名的利特尔-帕克斯磁阻振荡。在由两个约瑟夫森结组成的超导量子干涉器件（SQUID）中，临界电流的周期性变化导致不同类型的磁阻振荡，用于检测磁场的极小变化。在这里，我们展示了在没有约瑟夫森结的超导纳米环中，电流诱导的Little-Parks和SQUID磁阻振荡之间的切换。我们对Nb纳米环的测量表明，随着偏置电流的增加，抛物型Little-Parks磁阻振荡变为正弦振荡，并最终转变为典型的SQUID振荡。我们将这种现象与超导纳米环上的超导引线（“臂”）引起的磁致有序参数的不均匀性联系起来。在最小序参数点处，电流增强的相滑率在环中产生有效的约瑟夫森结，将其转换为SQUID。
The critical temperature in a superconducting ring changes periodically with the magnetic flux threading it, giving rise to the well-known Little-Parks magnetoresistance oscillations. Periodic changes of the critical current in a superconducting quantum interference device (SQUID), consisting of two Josephson junctions in a ring, lead to a different type of magnetoresistance oscillations utilized in detecting extremely small changes in magnetic fields. Here we demonstrate current-induced switching between Little-Parks and SQUID magnetoresistance oscillations in a superconducting nano-ring without Josephson junctions. Our measurements in Nb nano-rings show that as the bias current increases, the parabolic Little-Parks magnetoresistance oscillations become sinusoidal and eventually transform into oscillations typical of a SQUID. We associate this phenomenon with the flux-induced non-uniformity of the order parameter along a superconducting nano-ring, arising from the superconducting leads (‘arms’) attached to it. Current enhanced phase slip rates at the points with minimal order parameter create effective Josephson junctions in the ring, switching it into a SQUID.