Finite-Depth Interfacial Coupling in Metal/Topological Insulator van der Waals Heterostructures

Metal/topological insulator van der Waals (vdW) heterostructures offer a platform for engineering emergent quantum states beyond isolated layers. While proximity effects in covalently bonded systems are well studied, coupling depth across vdW interfaces remains unclear. Using angle-resolved photoemission spectroscopy and first-principles calculations, we investigate the thickness dependence of TiTe2/Bi2Te3 electronic states. Despite nominally weak vdW bonding, the buried interface induces emergent bands and splitting near a band crossing, consistent with hybridization. Interface-induced features persist in the bilayer, while band evolution nearly saturates in thicker films. Even at four layers, the electronic structure does not simply recover to the intrinsic TiTe2 limit, consistent with finite-depth coupling that substantially reshapes the overlayer bands. Charge redistribution and a moiré-modulated interfacial potential contribute to this reconstruction. Finite-depth coupling may be a hallmark of strongly coupled vdW heterostructures and guide topological and quantum electronic device design.