Anomalous normal state resistivity in superconducting $La_{2-x}Ce_xCuO_4$: Fermi liquid or strange metal?

Abstract

We present experimental results for the in-plane resistivity of the electron-doped cuprate superconductor $La_{2-x}Ce_xCuO_4$ above its transition temperature $T_c$ as a function of Ce doping x and temperature. For the doping x between 0.11 and 0.17, where $T_c$ varies from 30 K (x=0.11) to 5 K (x=0.17), we find that the resistivity shows an approximate $T^2$ behavior for all values of doping over the measurement range from 100 K to 400 K. The coefficient of the $T^2$ resistivity term decreases with increasing x following the trend in $T_c$. We analyze our data theoretically and posit that n-type cuprates are better thought of as strange metals. Although the quadratic temperature dependence appears to be in naive agreement with the Fermi liquid (FL) expectations, the fact that the measured resistivity is large and no phonon-induced linear-in-T resistivity manifests itself even at 400 K argue against a standard normal metal Fermi liquid picture being applicable. We discuss possible origins of the strange metal behavior.