Phenomenological classification of metals based on resistivity

Efforts to understand metallic behavior have led to important concepts such as those of strange metals, bad metals, or Planckian metals. However, a unified description of metallic resistivity is still missing. An empirical analysis of a large variety of metals shows that the parallel resistor formalism used in the cuprates, which includes T-linear and T-quadratic dependence of the electron scattering rates, can be used to provide a phenomenological description of the electrical resistivity in all metals. Here, we show that the different metallic classes are then determined by the relative magnitude of these two components and the magnitude of the extrapolated residual resistivity. These two parameters allow us to categorize a few systems that are notoriously hard to ascribe to one of the currently accepted metallic classes.