Similarity of Scattering Rates in Metals Showing T-Linear Resistivity

Quantum Critical Scattering The temperature (T) dependence of the electrical resistivity offers clues about the behavior of electrical carriers. One of the more puzzling observations is the T-linear resistivity found in systems known or suspected to exhibit quantum criticality, such as cuprate and organic superconductors, and heavy fermion materials; the origin of this behavior remains elusive. Bruin et al. (p. 804) find that the ruthenate Sr3Ru2O7 also exhibits T-linear resistivity in the vicinity of its quantum critical point, and that its scattering rate per kelvin is approximately given by the inverse of a characteristic time made up of the Planck and Boltzmann constants. A comprehensive analysis of other systems with T-linear resistivity, including ordinary metals at high temperatures, indicates that their scattering rates are similarly close to the characteristic rate. That the rates are similar across a wide range of materials with diverse microscopic scattering mechanisms may indicate universal behavior. Transport measurements show little variation across metals with resistivity that scales linearly with temperature. Many exotic compounds, such as cuprate superconductors and heavy fermion materials, exhibit a linear in temperature (T) resistivity, the origin of which is not well understood. We found that the resistivity of the quantum critical metal Sr3Ru2O7 is also T-linear at the critical magnetic field of 7.9 T. Using the precise existing data for the Fermi surface topography and quasiparticle velocities of Sr3Ru2O7, we show that in the region of the T-linear resistivity, the scattering rate per kelvin is well approximated by the ratio of the Boltzmann constant to the Planck constant divided by 2π. Extending the analysis to a number of other materials reveals similar results in the T-linear region, in spite of large differences in the microscopic origins of the scattering.