Tilted Dirac cones in two-dimensional materials: Impact on electron transmission and pseudospin dynamics

Abstract

This study is devoted to the profound implications of tilted Dirac cones on the quantum transport properties of two-dimensional (2D) Dirac materials. These materials, characterized by their linear conic energy dispersions in the vicinity of Dirac points, exhibit unique electronic behaviors, including the emulation of massless Dirac fermions and the manifestation of relativistic phenomena such as Klein tunneling. Expanding beyond the well-studied case of graphene, the manuscript focuses on materials with tilted Dirac cones, where the anisotropic and tilted nature of the cones introduces additional richness to their electronic properties that arises from an emergent underlying spacetime geometry. The investigation begins by considering a heterojunction of 2D Dirac materials, where electrons undergo quantum tunneling between regions with upright and tilted Dirac cones. The role of tilt in characterizing the transmission of electrons across these interfaces is thoroughly examined, shedding light on the influence of the tilt parameter on the transmission probability and the fate of the pseudospin of the Dirac electrons, particularly upon a sudden change in the tilting. We also investigate the probability of reflection and transmission from an intermediate slab with arbitrary subcritical tilt, focusing on the behavior of electron transmission across regions with varying Dirac cone tilts. The study demonstrates that for certain thicknesses of the middle slab, the transmission probability is equal to unity, and both reflection and transmission exhibit periodic behavior with respect to the slab thickness. This is reminiscent of Klein tunneling across scalar potential barriers in PNP junctions, no gate voltage is applied. Such a tilt-induced potential can be considered as the quantum transport manifestation of the "gravitomagnetic"effect of underlying spacetime structure. © 2024 American Physical Society.