作为量子引擎的约瑟夫森结
The Josephson junction as a quantum engine
AI总结：
该研究将约瑟夫森结视为量子引擎，通过建立弱耦合下的马尔可夫主方程描述其动力学特征，揭示自振荡与单色辐射的关联，解决相关开放问题并开辟新研究方向。
摘要：
我们将约瑟夫森结（JJ）超导电极中的库珀对视为一个开放系统，通过安德烈夫散射与外部电子库耦合。电子库之间的非平衡态产生了施加于JJ的直流偏置。在弱耦合极限下，我们得到了一个马尔可夫主方程，该方程提供了与JJ主要特征一致的简单动力学描述，包括电流-电压特性的形式、其磁滞现象，以及在周期性电压驱动下离散夏皮罗步的出现。对于小耗散情况，我们的模型还展现出JJ电偶极子在平均电压V附近以频率Ω=2eV/ℏ发生自振荡。这种与非线性运动方程的“隐藏吸引子”相关的自振荡，解释了观测到的频率为Ω及其谐波的单色辐射的产生。我们认为，这种将JJ视为量子引擎的图景解决了关于约瑟夫森效应作为不可逆过程的悬而未决的问题，并可能为量子热力学和动力系统理论开辟新的视角。
英文摘要：
We treat the Cooper pairs in the superconducting electrodes of a Josephson junction (JJ) as an open system, coupled via Andreev scattering to external baths of electrons. The disequilibrium between the baths generates the direct-current bias applied to the JJ. In the weak-coupling limit we obtain a Markovian master equation that provides a simple dynamical description consistent with the main features of the JJ, including the form of the current-voltage characteristic, its hysteresis, and the appearance under periodic voltage driving of discrete Shapiro steps. For small dissipation, our model also exhibits a self-oscillation of the JJ's electrical dipole with frequency $Ω= 2 e V / \hbar$ around mean voltage $V$. This self-oscillation, associated with "hidden attractors" of the nonlinear equations of motion, explains the observed production of monochromatic radiation with frequency $Ω$ and its harmonics. We argue that this picture of the JJ as a quantum engine resolves open questions about the Josephson effect as an irreversible process and could open new perspectives in quantum thermodynamics and in the theory of dynamical systems.
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