Tunneling photo-thermoelectric effect in monolayer graphene/bilayer hexagonal boron nitride/bilayer graphene asymmetric van der Waals tunnel junctions.

This article focuses on the demonstration of the tunneling photo-thermoelectric effect (TPTE) in a vertically stacked asymmetric tunnel junction composed of monolayer graphene (MLG), bilayer hexagonal boron nitride (h-BN), and bilayer graphene (BLG). By applying a perpendicular magnetic field under mid-infrared irradiation, the researchers induced cyclotron resonance (CR) absorption selectively in the MLG, creating an electron temperature difference between MLG and BLG that generated an out-of-plane photovoltage across the h-BN tunnel barrier. The TPTE differs from conventional in-plane photo-thermoelectric effects by producing voltage across the tunnel barrier, relying on asymmetric electrodes, and showing enhanced signals near transitions between quantum Hall states and non-quantum Hall states in MLG. This effect offers a novel approach for probing electronic and optoelectronic properties in two-dimensional material heterostructures.