Low Temperature Electronic Measurements in Novel Topological Insulator-Antiferromagnetic Insulator Thin Film Heterostructures.

Topological insulators (TIs) are of great interest for their unique combination of insulating bulk and metallic edge states. In 3D TIs, these edge states are spin polarized 2D conducting surface states protected from backscattering by time reversal symmetry. These states have great applicational potential in spintronic and quantum computing devices. The Dirac cone that forms at the surface of a 3D TI is robust to non-magnetic perturbations, but a gap can be opened through proximity to an ordered magnetic material. The insulating antiferromagnet nickel fluoride NiF₂ makes an interesting candidate for this proximity effect because of its weak ferromagnetic moment resulting from a spontaneous canting, in addition to terahertz frequency magnon fluctuations arising from the antiferromagnetic ordering. Our work shows how a NiF₂-3D TI interface can be epitaxially grown via molecular beam epitaxy and presents low temperature charge carrier measurements performed in these heterostructures. These experiments demonstrate these structures can be fabricated into thin film devices and presents a path forward for further study and manipulation of these topologically protected surface states.