Bulk-Surface Transport Separation and Topological Surface States Modulation of TI–TI Heterostructures

In this study, we prepare topological insulator (TI) heterostructures (TI–TI) with a thickness of 25 nm and various interlayer distances, utilizing the laser molecular beam epitaxy (LMBE) system. Our characterization analysis revealed high-quality morphological features and distinct heterolayered structures. Moreover, we successfully isolated bulk-surface transport properties by employing the comprehensive physical property measurement system (PPMS) and terahertz time-domain spectroscopy (THz-TDS). Compared to the monolayer binary structures, the TI–TI heterostructures demonstrated enhancement of the bulk insulation and improvement of surface conductivity. Notably, various interlayer spacings played a pivotal role in modulating both the bulk-surface transport and topological surface states. TIs have emerged as an ideal medium for information transmission in quantum chips, terahertz optical devices, and low-energy spintronic devices. This research not only provides deeper theoretical insights but also holds significant implications for practical applications.