Exchange Interaction-Driven Surface State Hybridization in Bi₂Se₃ Topological Insulator

Topological insulator has gapless surface state, which results from bulk band inversion due to strong spin-orbit coupling. This nontrivial topology robust to nonmagnetic disorders and defects is considered one of the biggest obstacles for modulations of the surface state. In this work, the suppression of surface properties in Bi2Se3 of various thicknesses grown on antiferromagnetic NiO, which has a strong exchange interaction is investigated. Under perpendicular magnetic fields, a drastic decrease in mobility mu and in the number of phase coherent channels alpha in 5 QL Bi2Se3 on NiO are observed. In addition, the THz transmission study shows that an increase in the surface penetration depth xi can accelerate the hybridization of surface states, which is also verified using the optical pump THz probe. This rapid collapse of surface states indicates the unique role of antiferromagnetic materials in band overlap, suggesting that the topological surface nature can be modulated by forming an antiferromagnet-topological insulator heterostructure.