Colossal Layer Nernst Effect in Twisted Moiré Layers

Intriguing Nernst effects offer the prospect of engineering micro- and nano-sized thermoelectric devices, facilitating heat harvesting, energy conversion, and directional temperature control. In this Letter, we establish a theoretical analysis of the layer Nernst effect (LNE) in twisted moiré layers subjected to a temperature gradient. Our analysis reveals the emergence of a layer-contrasted Nernst voltage perpendicular to the direction of the temperature gradient. This phenomenon arises from the trigonal warping of the Fermi surface and the layer pseudomagnetic field. The Fermi surface's trigonal warping, breaking intra-valley inversion symmetry, leads to an imbalance between left and right movers, resulting in a non-vanishing LNE. We validate our theoretical framework by applying it to twisted bilayer graphene (TBG). Importantly, our findings indicate that the Nernst coefficient in TBG can reach values as high as μA/K, surpassing those of previously known materials by three orders of magnitude. These results provide a foundation for utilizing TBG and other twisted moiré layers as promising platforms to explore layer caloritronics and develop thermoelectric devices.