In the linear regime, thermo-electric effects between two conductors are possible only in the presence of an explicit breaking of the electron-hole symmetry. We consider a tunnel junction between two electrodes and show that this condition is no longer required outside the linear regime. In particular, we demonstrate that a thermally-biased junction can display an absolute negative conductance (ANC), and hence thermo-electric power, at a small but finite voltage bias, provided that the density of states of one of the electrodes is gapped and the other is monotonically decreasing. We consider a prototype system that fulfills these requirements, namely a tunnel junction between two different superconductors where the Josephson contribution is suppressed. We discuss this nonlinear thermo-electric effect based on the spontaneous breaking of electron-hole symmetry in the system, characterize its main figures of merit and discuss some possible applications.

中文翻译：

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电子-空穴对称系统的非线性热电

在线性状态下，只有在明显破坏电子-空穴对称性的情况下，两个导体之间的热电效应才可能发生。我们考虑了两个电极之间的隧道结，并表明在线性范围之外不再需要这种情况。特别地，我们证明了热偏置结可以显示出绝对的负电导（ANC），因此，只要电极之一的状态密度处于间隙且另一个在单调下降。我们考虑一个满足这些要求的原型系统，即两个不同超导体之间的隧道结，从而抑制了约瑟夫森的贡献。