Quantum coherent control of nonlinear thermoelectric transport in a triple-dot Aharonov-Bohm heat engine
arxiv(2023)
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∼
2.35 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∼ 3.85 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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关键词
coherent control,quantum,non-linear,triple-dot,aharonov-bohm
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