Nanoscale Mid-Infrared Near-Field Tomography of Topological Insulator Surfaces

Three-dimensional topological insulators (TIs) have become an interesting platform for future high-speed electronics. The massless Dirac fermions in topologically protected surface states (TSSs) feature a chiral spin texture, which gives rise to inherently low scattering rates [1,2]. However, an additional two-dimensional electron gas (2DEG) with finite mass at TI surfaces can coexist under ambient conditions [3] owing to band bending effects.