Integrating three-dimensional topological materials into advanced electronic architectures offers a path toward added functionality through low-power quantum devices if we resolve fundamental engineering concerns regarding preferential carrier injection into quantum channels. Using the self-consistent nonequilibrium Green's function approach, we investigate the impact of symmetry protection and low density of states on carrier dynamics at the metal-topological interface. We demonstrate that the topological surface state (TSS) acts as an electrostatic screen, fundamentally altering traditional semiconductor physics: in the diffusive regime $({\varphi }_{\mathrm{MS}}<-0.2\mathrm{eV})$, the TSS results in a significantly reduced diffusion length compared to trivial insulators; in the depletion regime $({\varphi }_{\mathrm{MS}}>-0.2\mathrm{eV})$, the TSS limits the depletion width while facilitating the isolation of surface conduction through the quantum channel. Furthermore, we show that the introduction of magnetic scattering at the interface further enhances injection by hybridizing metallic and topological states. These findings establish application-specific design rules for topological interconnects, enabling the isolation or flooding of surface channels through work-function and interface engineering.

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• Capacitance
• Depletion interactions
• Electrical conductivity
• Surface states
• Topological metamaterials
• Device fabrication
• Interfaces
• Metals
• Surfaces
• Topological insulators
• Tight-binding model