Anomalous Criticality in the Electrical Resistivity of La2-xSrxCuO4

The presence or absence of a quantum critical point and its location in the phase diagram of high-temperature superconductors have been subjects of intense scrutiny. Clear evidence for quantum criticality, particularly in the transport properties, has proved elusive because the important low-temperature region is masked by the onset of superconductivity. We present measurements of the low- temperature in- plane resistivity of several highly doped La2-xSrxCuO4 single crystals in which the superconductivity had been stripped away by using high magnetic fields. In contrast to other quantum critical systems, the resistivity varies linearly with temperature over a wide doping range with a gradient that scales monotonically with the superconducting transition temperature. It is maximal at a critical doping level (p(c)) similar to 0.19 at which superconductivity is most robust. Moreover, its value at pc corresponds to the onset of quasi- particle incoherence along specific momentum directions, implying that the interaction that first promotes high- temperature superconductivity may ultimately destroy the very quasi- particle states involved in the superconducting pairing.