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arXiv 1906.09191cond-mat.quant-gas
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量子点接触中的玻色子超流输运

Bosonic superfluid transport in a quantum point contact

Shun Uchino, Jean-Philippe Brantut

摘要:

本文提出了量子点接触中相互作用的低温玻色-爱因斯坦凝聚体的热输运和粒子输运的微观理论。我们发现,在相反的收费,费米子超导体,玻色子系统的特点隧穿过程的凝聚元素,导致存在的奇阶谐波的交流约瑟夫森电流。一个至关重要的作用是由一个异常的隧穿过程中凝聚元素相干转换成声子激发,导致偶次谐波的交流电流以及直流贡献。在低偏压下,我们发现耗散组件遵守欧姆定律,和偏压无关的非耗散组件,形成鲜明对比的费米超导体。分析直流贡献,我们发现零热电势和洛伦兹数在零温度下,玻色子Wiedemann-Franz定律的崩溃。这些结果突出了电荷中性超流体固有的异常隧穿过程的重要性。在现有的冷原子传输装置中可以很容易地观察到其后果。

英文摘要:

We present a microscopic theory of heat and particle transport of an interacting, low temperature Bose-Einstein condensate in a quantum point contact. We show that, in contrast to charged, fermionic superconductors, bosonic systems feature tunneling processes of condensate elements, leading to the presence of odd-order harmonics in the AC Josephson current. A crucial role is played by an anomalous tunneling process where condensate elements are coherently converted into phonon excitations, leading to even-order harmonics in the AC currents as well as a DC contribution. At low bias, we find dissipative components obeying Ohm's law, and bias-independent nondissipative components, in sharp contrast to fermionic superconductors. Analyzing the DC contribution, we find zero thermopower and Lorenz number at zero temperature, a breakdown of the bosonic Wiedemann-Franz law. These results highlight importance of the anomalous tunneling process inherent to charge neutral superfluids. The consequences could readily be observed in existing cold-atom transport setups.

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