Sonar Vrishali, Trocha Piotr
Institute of Spintronics and Quantum Information, Faculty of Physics and Astronomy, Adam Mickiewicz University, Poznan, 61-614, Poland.
Sci Rep. 2025 Apr 25;15(1):14509. doi: 10.1038/s41598-025-94991-2.
We investigate the thermoelectric response of a hybrid system consisting of two ferromagnetic electrodes and one superconducting lead coupled to a single-level quantum dot with finite Coulomb repulsion. Using the non-equilibrium Green's function technique within the Hubbard-I approximation, local and non-local thermoelectric coefficients, along with their spin counterparts, such as electrical and thermal conductance, and the Seebeck coefficient are calculated up to linear order with respect to generalized forces. Here, we present a derivation of spin-dependent thermoelectric coefficients for a three-terminal system, extending the existing theory which allowed to describe only cases independent of spin-bias voltage, i.e. when spin accumulation is irrelevant. In the considered system, four competing processes- single particle tunneling, quasiparticle tunneling, direct and crossed Andreev reflection make the system highly adaptable for tuning charge and heat currents. A full analysis of their impact on thermoelectric effects is provided. Moreover, the output power and efficiency of the system operating as a heat engine are evaluated. The extensive goal of this work is to demonstrate how the presence of an additional terminal modifies the hybrid QD-based device's performance and under which conditions non-local thermoelectric effects become significant.
我们研究了一个混合系统的热电响应，该系统由两个铁磁电极和一个超导引线组成，耦合到一个具有有限库仑排斥作用的单能级量子点。使用哈伯德 - I近似下的非平衡格林函数技术，计算了局部和非局部热电系数及其自旋对应物，如电导率、热导率和塞贝克系数，直至相对于广义力的线性阶数。在这里，我们给出了一个三端系统自旋相关热电系数的推导，扩展了现有的理论，现有理论仅允许描述与自旋偏置电压无关的情况，即自旋积累无关紧要的情况。在所考虑的系统中，四个竞争过程——单粒子隧穿、准粒子隧穿、直接和交叉安德烈夫反射，使系统高度适合于调节电荷和热流。提供了对它们对热电效应影响的全面分析。此外，还评估了作为热机运行的系统的输出功率和效率。这项工作的广泛目标是展示额外终端的存在如何改变基于混合量子点的器件性能，以及在哪些条件下非局部热电效应变得显著。
