论文标题
在热平衡中的相位超导体正常环中的超电流噪声
Supercurrent Noise in a Phase-Biased Superconductor-Normal Ring in Thermal Equilibrium
论文作者
论文摘要
在超导体非正常抗管器（SNS）连接中，无耗散超电流是通过两个超导体之间相差控制的Andreev结合状态（ABS）介导的。长期以来，由于ABS之间的热激发，理论长期以来一直预测了这种超流动性的显着波动，因此是噪声。通过波动 - 散落定理（FDT），即使在零频率限制下，也矛盾地导致耗散电导。在本文中，我们直接测量了相位偏置的SNS环中的超电流噪声，该噪声与超导谐振器相结合。使用相同的设置，我们还测量了其入学率，并定量证明了任何阶段的FDT。耗散电导显示了1/t温度的依赖性，与未焦化金属的drude电导相反。即使在Andreev Spectrum无处不在的相位$π$上，这也是如此。在线性响应理论的支持下，我们将其归因于在费米级别对称对称之间的增强电流相关性。我们的结果提供了对液体超导设备中噪声的起源的洞察力，这可能对探测受拓扑保护的ABS有用。
In superconductor-normal-superconductor (SNS) junctions, dissipationless supercurrent is mediated via Andreev bound states (ABSs) controlled by the phase difference between the two superconductors. Theory has long predicted significant fluctuations, and thus a noise, of such supercurrent in equilibrium, due to the thermal excitation between the ABSs. Via the fluctuation-dissipation theorem (FDT), this leads paradoxically to a dissipative conductance even in the zero frequency limit. In this article, we directly measure the supercurrent noise in a phase-biased SNS ring inductively coupled to a superconducting resonator. Using the same setup, we also measure its admittance and quantitatively demonstrate the FDT for any phase. The dissipative conductance shows an 1/T temperature dependence, in contrast to the Drude conductance of unproximitized metal. This is true even at phase $π$ where the Andreev spectrum is gapless. Supported by linear response theory, we attribute this to the enhanced current correlation between the ABSs symmetrical across the Fermi level. Our results provide insight into the origin of noise in hydrid superconducting devices which may be useful for probing topologically protected ABSs.
