Anomalous Fermi liquid behavior of overdoped high-Tcsuperconductors

Abstract

According to a generic temperature versus carrier-doping $(T\text{\ensuremath{-}}p)$ phase diagram of high-temperature superconductors (HTSC), it has been proposed that as doping increases to the overdoped region, they approach gradually a conventional (canonical) Fermi liquid. However, Hall effect measurements in several systems reported by different authors show a still strong $T$ dependence in overdoped samples. We report here electrical transport measurements of ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ thin films presenting a temperature dependence of the Hall constant, ${R}_{H}$, which does not present a gradual transition towards the $T$-independent behavior of a canonical Fermi liquid. Instead, the $T$ dependence passes by a minimum near optimal doping and then increases again in the overdoped region. We discuss the theoretical predictions from two representative Fermi liquid models and show that they cannot give a satisfactory explanation to our data. We conclude that this region of the phase diagram in YBCO, as in most HTSC, is not a canonical Fermi liquid, therefore we call it an anomalous Fermi liquid.