Sign-Alternating Thermoelectric Quantum Oscillations in Insulating Monolayer WTe

The detection of Landau-level-like energy structures near the chemical potential of an insulator is essential to the search for a class of correlated electronic matter hosting charge-neutral Fermi surfaces, a long-proposed concept that remains elusive experimentally. In this talk we will introduce and demonstrate that the magneto-thermoelectric response of a quantum insulator can reveal critical information not available via other approaches. We report large quantum oscillations (QOs) in the Seebeck response of the hole-doped insulating state of monolayer tungsten ditelluride (WTe₂) in magnetic fields. The QOs undergo sign-changes as the field is swept, which implies the presence of a field-induced Landau-level-like structure at the chemical potential of the insulator. We will discuss the implications of the observation in the context of different interpretations.