Attaining viable thermoelectric cooling at cryogenic temperatures is of considerable fundamental and technological interest for electronics and quantum materials applications. In-device temperature control can provide more efficient and precise thermal environment management compared with conventional global cooling. The application of a current and perpendicular magnetic field gives rise to cooling by generating electron–hole pairs on one side of the sample and to heating due to their recombination on the opposite side, which is known as the Ettingshausen effect. Here we develop nanoscale cryogenic imaging of the magneto-thermoelectric effect and demonstrate absolute cooling and an Ettingshausen effect in exfoliated WTe₂ Weyl semimetal flakes at liquid He temperatures. In contrast to bulk materials, the cooling is non-monotonic with respect to the magnetic field and device size. Our model of magneto-thermoelectricity in mesoscopic semimetal devices shows that the cooling efficiency and the induced temperature profiles are governed by the interplay between sample geometry, electron–hole recombination length, magnetic field, and flake and substrate heat conductivities. The observations open the way for the direct integration of microscopic thermoelectric cooling and for temperature landscape engineering in van der Waals devices.

在低温下实现可行的热电冷却对于电子和量子材料应用具有相当大的基础和技术意义。与传统的全局冷却相比，设备内温度控制可以提供更高效、更精确的热环境管理。施加电流和垂直磁场会通过在样品的一侧产生电子-空穴对来产生冷却，并由于它们在另一侧的复合而产生加热，这被称为埃廷斯豪森效应。在这里，我们开发了磁热电效应的纳米级低温成像，并证明了在液氦温度下剥离的WTe _{2 Weyl半金属薄片的绝对冷却和埃廷斯豪森效应。}与散装材料相比，冷却对于磁场和器件尺寸来说是非单调的。我们的介观半金属器件磁热电模型表明，冷却效率和感应温度分布受样品几何形状、电子-空穴复合长度、磁场以及薄片和基底热导率之间的相互作用控制。这些观察结果为微观热电冷却的直接集成和范德华装置中的温度景观工程开辟了道路。