Oberflächenbänder

Oberflächenbänder, also known as surface bands, are a phenomenon observed in condensed matter physics, particularly in the context of topological materials. These bands are electronic states that are localized to the surface or interfaces of a material, as opposed to the bulk of the material. They arise due to the breaking of inversion symmetry at the surface, leading to a distinct electronic structure compared to the bulk.

The existence of surface bands is a key characteristic of topological insulators. In these materials, the bulk possesses an insulating electronic band gap, meaning there are no electronic states available for conduction within the bulk. However, the surface states of topological insulators are metallic, allowing for electrical conductivity along the surface. This unique property arises from the topological nature of the bulk electronic wavefunctions, which cannot be smoothly deformed into the wavefunctions of a trivial insulator without closing and reopening the band gap.

Surface bands can also occur in other types of materials, such as two-dimensional materials like graphene, where the electronic properties are inherently confined to a surface. The study of Oberflächenbänder is crucial for understanding the exotic electronic behavior of topological materials and has potential applications in areas like spintronics and quantum computing. Their topological protection often makes them robust against certain types of disorder.