Thermoelectric effects in metals are typically small due to the nearly perfect particle–hole symmetry around their Fermi surface. Furthermore, thermo-phase effects and linear thermoelectricity in superconducting systems have been identified only when particle–hole symmetry is explicitly broken, since thermoelectric effects were considered impossible in pristine superconductors. Here, we experimentally demonstrate that superconducting tunnel junctions develop a very large bipolar thermoelectricity in the presence of a sizable thermal gradient thanks to spontaneous particle–hole symmetry breaking. Our junctions show Seebeck coefficients of up to ±300 μV K^–1, which is comparable with quantum dots and roughly 10⁵ times larger than the value expected for normal metals at subkelvin temperatures. Moreover, by integrating our junctions into a Josephson interferometer, we realize a bipolar thermoelectric Josephson engine generating phase-tunable electric powers of up to ~140 nW mm^–2. Notably, our device implements also the prototype for a persistent thermoelectric memory cell, written or erased by current injection. We expect that our findings will lead to applications in superconducting quantum technologies.

金属中的热电效应通常很小，因为它们的费米表面周围几乎完美的粒子-空穴对称。此外，超导系统中的热相效应和线性热电只有在粒子-空穴对称性被明确破坏时才被识别，因为在原始超导体中热电效应被认为是不可能的。在这里，我们通过实验证明，由于自发的粒子-空穴对称性破坏，在存在相当大的热梯度的情况下，超导隧道结会产生非常大的双极热电。我们的结显示高达 ±300 μV K ^–1的塞贝克系数，与量子点相当，大约为 10 ⁵比正常金属在亚开尔文温度下的预期值大几倍。此外，通过将我们的结集成到约瑟夫森干涉仪中，我们实现了双极热电约瑟夫森引擎，可产生高达~14​​0 nW mm ^–2的相位可调电功率。值得注意的是，我们的设备还实现了持久热电存储单元的原型，通过电流注入写入或擦除。我们预计我们的发现将导致在超导量子技术中的应用。