Unconventional Materials: the mismatch between electronic charge centers and atomic positions

Understand

The complete band representations (BRs) have been constructed in the work of topological quantum chemistry.

• Each BR is expressed by either a localized orbital at a Wyckoff site in real space, or by a set of irreducible representations in momentum space.
• In this work, we define unconventional materials with a common feature of the mismatch between average electronic centers and atomic positions.
• They can be effectively diagnosed as whose occupied bands can be expressed as a sum of elementary BRs (eBRs), but not a sum of atomic-orbital-induced BRs (aBRs).