Planckian relaxation delusion in metals

We present a critical review of recent attempts to introduce a new quantum (‘Planckian’) limit for the temperature dependence of the inelastic scattering rate of electrons in metals. We briefly discuss the main experimental facts and some simple theoretical models explaining the linear-in-temperature growth of resistivity (starting from very low temperatures) in superconducting cuprates and some similar systems. There is no commonly accepted theoretical explanation for such behavior up to now. We also discuss the known quantum limits for electrical conductivity (resistance). It is shown that the universal Planckian limit for the inelastic relaxation rate proposed in some papers is a kind of delusion related to a certain procedure to represent the experimental data.