Anisotropic scattering and anomalous normal-state transport in a high-temperature superconductor

The metallic state of high-temperature copper-oxide superconductors, characterized by unusual and distinct temperature dependences in the transport properties1,2,3,4, is markedly different from that of textbook metals. Despite intense theoretical efforts5,6,7,8,9,10,11, our limited understanding is impaired by our inability to determine experimentally the temperature and momentum dependence of the transport scattering rate. Here, we use a powerful magnetotransport probe to show that the resistivity and the Hall coefficient in highly doped Tl2Ba2CuO6+δ originate from two distinct inelastic scattering channels. One channel is due to conventional electron–electron scattering; the other is highly anisotropic, has the same symmetry as the superconducting gap and a magnitude that grows approximately linearly with temperature. The observed form and anisotropy place tight constraints on theories of the metallic state. Moreover, in heavily doped non-superconducting La2−xSrxCuO4, this anisotropic scattering term is absent12, suggesting an intimate connection between the origin of this scattering and superconductivity itself.