Quantum point junction on the surface of an antiferromagnetic topological insulator

Engineering and manipulation of unidirectional channels has been achieved in quantum Hall systems, leading to the construction of electron interferometers and giving rise to the field of electron quantum optics. However, these material systems require strong external magnetic fields and ultra low temperatures to be realized, which limits their applicability in microelectronic applications. In addition, mixing and interference of edge-state wave functions is achieved by bringing two channels in close proximity to enable tunneling. These so-called quantum point contacts are highly sensitive to their local environment and are hard to tune. In this work, we find that antiferromagnetic topological insulators offer a novel opportunity to realize robust and controllable quantum point junctions due to existence of two distinct types of gapless unidirectional channels, one from antiferromagnetic domain walls and the other from single-height steps. Their distinct geometric nature allows them to intersect robustly to form quantum point junctions, which then enables their control by magnetic and electrostatic local probes. Encouraged by the recent progress in material realization, the existence of stable and tunable junctions, the intrinsic magnetism, and the potential for higher-temperature performance we propose antiferromagnetic topological insulators as a new promising platform for electron quantum optics.