Spin caloritronics with superconductors: Enhanced thermoelectric effects, generalized Onsager response-matrix, and thermal spin currents
Spin caloritronics with superconductors: Enhanced thermoelectric effects, generalized Onsager response-matrix, and thermal spin currents
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DOI：
10.1103/physrevb.93.224509
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发表时间：
2016-06-08
影响因子：
3.7
通讯作者：
Bathen, Marianne Etzelmueller
中科院分区：
文献类型：
--
作者：
Linder, Jacob;Bathen, Marianne Etzelmueller
最近有人提出并实验证明，由于自旋相关的粒子-空穴不对称性，在铁磁体/超导体结构中产生大的热电效应是可能的。在这里，我们从理论上证明了两个自旋分裂超导体之间的准粒子隧穿与仅使用一个这样的超导体时相比，增强了热电响应许多倍，产生的塞贝克系数（S > 1 mV/K）和品质因数（ZT接近或等于40）远远超过最好的大块热电材料，并且它也变得对非弹性散射过程更具弹性。我们提出了一个广义Onsager响应矩阵，考虑到自旋相关的电压和温度梯度。此外，我们表明，热诱导的自旋电流在这样的结中创建，即使在没有极化隧穿势垒，也成为最大的情况下，其中自旋依赖的粒子-空穴不对称性存在于两侧的障碍。我们确定如何这些热自旋电流可以调谐的幅度和符号的几个参数，包括外部场，温度和超导相位差。
It has recently been proposed and experimentally demonstrated that it is possible to generate large thermoelectric effects in ferromagnet/superconductor structures due to a spin-dependent particle-hole asymmetry. Here, we show theoretically that quasiparticle tunneling between two spin-split superconductors enhances the thermoelectric response manyfold compared to when only one such superconductor is used, generating Seebeck coefficients (S > 1 mV/K) and figures of merit (ZT similar or equal to 40) far exceeding the best bulk thermoelectric materials, and it also becomes more resilient toward inelastic-scattering processes. We present a generalized Onsager response-matrix that takes into account spin-dependent voltage and temperature gradients. Moreover, we show that thermally induced spin currents created in such junctions, even in the absence of a polarized tunneling barrier, also become largest in the case in which spin-dependent particle-hole asymmetry exists on both sides of the barrier. We determine how these thermal spin-currents can be tuned both in magnitude and sign by several parameters, including the external field, the temperature, and the superconducting phase difference.