非相干MAR区扩散SNS结中的电流噪声
Current noise in diffusive SNS junctions in the incoherent MAR regime (a review)
摘要：
我们提出了一个理论的电流散粒噪声在任意温度下的低电阻界面长扩散SNS结构。在这样的结构中，噪声主要由N区中的正常电子散射产生。尽管$I$ - $V$特性近似由欧姆定律描述，但电流噪声揭示了MAR状态的所有特征：低电压下的“巨大”增强、显著的SGS和高电压下的过量噪声。非相干MAR区噪声的最显著特征是在零电压和零温度下的通用有限噪声电平$S= 4Δ/3R$。这种效应可以被理解为载流子的有效电荷$q^{\it eff}=2Δ/V$的增强的结果，或者，可替代地，被理解为具有有效温度$T_0=Δ/3$的能隙区域中的强非平衡准粒子布居的效应。在电子-电子散射占主导地位的条件下，结发生了向热电子区的过渡，亚带隙电子的有效温度随电压的增加呈指数下降。根据非相干MAR的电路理论计算了噪声功率。
英文摘要：
We present a theory for the current shot noise in long diffusive SNS structures with low-resistive interfaces at arbitrary temperatures. In such structures, the noise is mostly generated by normal electron scattering in the N-region. Whereas the $I$-$V$ characteristics are approximately described by Ohm's law, the current noise reveals all characteristic features of the MAR regime: "giant" enhancement at low voltages, pronounced SGS, and excess noise at large voltages. The most spectacular feature of the noise in the incoherent MAR regime is a universal finite noise level at zero voltage and at zero temperature, $S= 4Δ/3R$. This effect can be understood as the result of the enhancement of the effective charge of the carriers, $q^{\it eff}=2Δ/V$, or, alternatively, as the effect of strongly non-equilibrium quasiparticle population in the energy gap region with the effective temperature $T_0=Δ/3$. Under the condition of dominant electron-electron scattering, the junction undergoes crossover to the hot electron regime, with the effective temperature of the subgap electrons decreasing logarithmically with the voltage. Calculation of the noise power has been done on the basis of circuit theory of the incoherent MAR.
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