Semimetallike

Semimetallike is a descriptive term used in solid-state physics and materials science to describe materials whose electronic structure and transport properties resemble those of semimetals, without a strict classification as a semimetal. The phrase is often applied to systems where the conduction and valence bands nearly touch or slightly overlap, resulting in a very small carrier concentration at the Fermi level and a coexistence of electron-like and hole-like carriers.

Electronic structure in semimetallike materials resembles that of true semimetals, with features such as a near touch point between the valence-band maximum and the conduction-band minimum, small Fermi surfaces, and sometimes Dirac or Weyl-like band crossings. Such materials can display compensated electronic structure, where electron and hole densities are comparable, leading to unique transport phenomena despite low overall conductivity.

Transport and optical properties often reflect the semimetallic character. Semimetallike substances can exhibit high carrier mobility, unusual magnetoresistance, and anisotropic conduction. Optical responses may extend into the infrared due to the small energy scales involved, and the absence of a sizable band gap influences absorption and reflectivity.

Examples typically associated with semimetallike behavior include elemental bismuth and antimony, and the layered carbon forms graphite and graphene, which show semimetallic transport in many regimes. Some topological materials and Dirac- or Weyl-semimetals are described as semimetal-like because of their band topology and low carrier concentration.

Note that semimetallike is an informal, flexible descriptor. Precise classification relies on band-structure calculations, carrier-density measurements, and a material’s response to temperature, pressure, and doping.