Valley aspect of lateral tunneling transport

Abstract

We theoretically study the valley aspect of lateral tunneling transport in valleytronic materials, using AB-stacked (Bernal-stacked) bilayer graphene as a material example. A lateral structure with multiple well/barrier interfaces is considered. A full-zone tight-binding method is employed, allowing for the study of intervalley mixing in electron states. We study the degree of tunneling current valley contrast under the condition of a source-drain bias or barrier asymmetry. For a single-barrier structure, it is found that the intervalley mixing is negligible, and the contrast is positively correlated with the barrier width and height. For a double-barrier structure, the effect of resonant tunneling is investigated. The intervalley mixing is shown to be significantly enhanced at resonant tunneling. In addition, the resonant levels are found valley split, and a proposal is given which exploits the splitting for the generation of a sizable tunneling current valley polarization. Based on a simple model using momentum-shifted thermal distribution for obliquely incident electrons, the temperature dependence of tunneling current valley polarization is also examined. An interesting crossover from the valley-orbit interaction-dominant polarization to the warping-dominant polarization is found to occur as the temperature is increased.