arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.06867cond-mat.mes-hallcond-mat.supr-con
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邻近效应在正常金属准粒子陷阱中的作用

Role of the proximity effect for normal-metal quasiparticle traps

R. P. Schmit, F. K. Wilhelm

摘要:

由于超导部分存在非平衡准粒子,许多超导器件的性能会下降。一种有希望的方法是使用正常金属准粒子陷阱,使正常金属与超导体形成良好的金属接触。利用带有这种陷阱的电压偏置正常金属-绝缘体-超导体结,研究了这种结的俘获性能以及超导邻近效应在其中所起的作用。这涉及到一个适当的一维模型的结和Usadel方程描述的超导体的非平衡态的数值解。陷阱的功能由隧道势垒处的态密度(DOS)决定。在此,邻近效应导致两个对抗性的特性影响的捕获性能:在能量$|E| = Δ_{\text{BCS}}$的DOS的有益的减少与光谱能隙的收缩引起准粒子中毒。对于这两种效果,捕集器位置是决定性的,这需要被考虑以优化捕集性能。此外,还研究了超导体内部耗散正常电流与超导电流之间的转换及其对准粒子密度的影响。

英文摘要:

The performance of many superconducting devices is degraded in presence of non-equilibrium quasiparticles in the superconducting part. One promising approach towards their evacuation is the use of normal-metal quasiparticle traps, where normal metal is brought into good metallic contact with the superconductor. A voltage biased normal-metal--insulator--superconductor junction equipped with such a trap is used to investigate on the trapping performance and the part played by the superconducting proximity effect therein. This involves an appropriate one-dimensional model of the junction and the numerical solution of Usadel equations describing the non-equilibrium state of the superconductor. The functionality of the trap is determined by the density of states (DOS) at the tunnel barrier. Herein, the proximity effect leads to two antagonistic characteristics affecting the trapping performance: the beneficial reduction of the DOS at an energy $|E| = Δ_{\text{BCS}}$ versus the contraction of the spectral energy gap causing quasiparticle poisoning. For both effects the trap position is decisive, which needs to be taken into account for optimizing the trapping performance. In addition, the conversion between dissipative normal and supercurrent inside the superconducting part with its impact on the quasiparticle density is studied.

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