Gate Tunable Dimensional Crossover of Quantum Confined Dirac Fermions.

Dimensionality fundamentally dictates the behavior of quantum systems, and dimensional crossover serves as a key bridge to understand the pronounced differences between distinct dimensional regimes. However, achieving continuous control over such a crossover within a real material remains challenging. Here, we demonstrate a gate-tunable dimensional crossover of quantum confined Dirac Fermions in graphene/transition metal dichalcogenide heterostructure quantum dots (QDs). By adjusting the electrostatic gate, we modulate the potential depth of an elongated QD, which exhibits distinct confinement sizes along two perpendicular directions, thereby enabling precise tuning of the confined carrier wavelength with respect to these two distinct size dimensions. Scanning tunneling microscopy measurements reveal a clear evolution from one-dimensional confinement, characterized by strongly anisotropic wave function distributions, to two-dimensional behavior. This establishes a direct and tunable means to control dimensional crossover in situ via electrostatic gating, providing a new platform for exploring dimension-driven quantum phenomena.