Large valley Nernst effect in twisted multilayer graphene systems

Valley Nernst effect is a newly proposed and experimentally confirmed effect, which could be used to design novel thermoelectric devices. We study the valley Nernst effect in ( M + N )-layer twisted multilayer graphene systems by a simple low-energy effective model. It is found that the total valley Nernst coefficient (VNC) is three orders of magnitude larger than that in monolayer group-VI dichalcogenides. The total VNC increases with the increase of layer numbers. It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy. We identify that the central peak is always negative stemming from the flat band. Two shoulder peaks are positively induced by the conduction and valence bands, respectively. These predicted features can be tested experimentally. The present work would shed more light on valley caloritronics.