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arXiv 2303.09202cond-mat.mes-hall
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三量子点 Aharonov-Bohm 热机中非线性热电输运的量子相干控制

Quantum coherent control of nonlinear thermoelectric transport in a triple-dot Aharonov-Bohm heat engine

Jayasmita Behera, Salil Bedkihal, Bijay Kumar Agarwalla, Malay Bandyopadhyay

发表信息：
Phys. Rev. B 108, 165419 (2023)
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AI总结：

本文研究三量子点 Aharonov-Bohm 热机中量子相干与高次谐波对非线性热电输运的影响，发现 AB 相位为 π/2 且点间隧穿与点-导线耦合相当时可实现最优效率与功率，并揭示几何不对称和宽带极限条件可进一步提升功率输出。

摘要：

我们研究了一个双端三角形三量子点 Aharonov-Bohm（AB）干涉仪中，由多路径干涉产生的量子相干性和高次谐波在非线性热电输运中的作用。我们量化了一个简单装置在非线性区域中效率与功率之间的权衡，该装置由三个无相互作用的量子点（其中两个连接到两个偏置金属库）组成，它们位于等边三角形的顶点，磁通量 $Φ$ 垂直穿过该三角形。对于空间对称的装置，当点间隧穿强度与点-导线耦合相当且 AB 相位 $ϕ=π/2$ 时，我们实现了最优效率和功率输出。我们的分析表明，高次谐波的存在是实现最优功率输出的必要但非充分条件。由单位透射的三个密排共振峰所代表的最大相长干涉可以将功率输出（$P_{max}\sim 2.35\\,\mathrm{fW}$）提高到仅有一个通道参与输运情况下的近 3.5 倍，相应的效率约为 $0.80η_{c}$，其中 $η_{c}$ 是卡诺效率。我们还研究了几何不对称性及其对效率和功率输出的影响。以源端和漏端耦合比（$x$）为特征的不对称装置，在 $x=1.5$ 时可以将最大功率输出进一步提高到 $P_{max}\sim 3.85\\,\mathrm{fW}$，且效率与对称情况相同。我们的研究表明，输出功率和效率在宽带极限下是最优的。对于窄带情况，功率输出显著降低。另一方面，无序效应会从根本上降低热机的性能。

英文摘要：

We investigate the role of quantum coherence and higher harmonics resulting from multiple-path interference in nonlinear thermoelectricity in a two-terminal triangular triple-dot Aharonov-Bohm (AB) interferometer. We quantify the trade-off between efficiency and power in the nonlinear regime of our simple setup comprising three non-interacting quantum dots (two connected to two biased metallic reservoirs) placed at the vertex of an equilateral triangle, and a magnetic flux $Φ$ pierces it perpendicularly. For a spatially symmetric setup, we achieve optimal efficiency and power output when the inter-dot tunneling strength is comparable to the dot-lead coupling, AB phase $ϕ=π/2$. Our analysis reveals that the presence of higher harmonics is necessary but not sufficient to achieve optimal power output. The maximal constructive interference represented by three close-packed resonance peaks of the unit transmission can enhance the power output ($P_{max}\sim 2.35\,\mathrm{fW}$) almost 3.5 times as compared to the case where only a single channel participates in the transport, and the corresponding efficiency is about $0.80η_{c}$ where $η_{c}$ is the Carnot efficiency. Geometric asymmetries and their effects on efficiency and power output are also investigated. An asymmetric setup characterized by the ratio of the coupling to the source and the drain terminals ($x$) can further enhance the maximum power output $P_{max}\sim 3.85\,\mathrm{fW}$ for $x=1.5$ with the same efficiency as that of the symmetric case. Our investigation reveals that the output power and efficiency are optimal in the wide-band limit. The power output is significantly reduced for the narrow-band case. On the other hand, disorder effects radically reduce the performance of the heat engine.

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