graphene is aligned to one of the hBN layers, we demonstrate the presence of additional sign reversals in the thermopower as a function of carrier density, directly evidencing the presence of the singlealigned moire superlattice. We show that the temperature dependence of the thermopower enables the assessment of the role of built-in strain variation and van Hove singularities and hints at the presence of Umklapp electron-electron scattering processes. As the thermopower peaks around the neutrality point, this allows to probe the energy spectrum degeneracy. Further, when graphene is double-aligned with the top and bottom hBN crystals, the thermopower exhibits features evidencing multiple cloned Dirac points caused by the differential super-moire superlattice. For both cases we evaluate how well the thermopower agrees with Mott’s equation. Finally, we show the same moire superlattice device can exhibit a temperature-driven thermopower reversal from positive to negative and vice versa, by controlling the carrier density. The study of thermopower provides an alternative approach to study the electronic structure of 2D superlattices, whilst offering opportunities to engineer the thermoelectric response on these heterostructures.
|Journal||Physical Review B|
|Publication status||Accepted/In press - 11 Aug 2023|