Electron-hole symmetry in quasiparticle spectral weight of cuprates observed via infrared and photoemission spectroscopy

We performed an optical spectroscopy study of single crystals of Pr0.85LaCe0.15CuO4-δ (PLCCO) to revisit the electron-hole asymmetry, which has been understood as a fundamental property of cuprates. Four differently annealed samples-as-grown, reduced, optimally oxygenated, and overoxygenated samples-were prepared, which have superconducting transition temperatures Tc=0, 15, 24, and 18 K, respectively. We observed that the low-energy quasiparticle spectral weights of all the PLCCO samples are significantly small in comparison with those of other electron-doped cuprate families. Instead, they are rather close to those of their hole-doped counterpart La2-xSrxCuO4. Accordingly, estimated effective carrier numbers Neff per Cu atom of superconducting samples are also very small, despite their relatively high critical temperatures. A complementary photoemission study reveals that the low-energy quasiparticle spectral weight of PLCCO is much smaller than that of Nd1.85Ce0.15CuO4-δ, consistent with the optical results. Our observations demonstrate that PLCCO provides the electron-hole symmetry in the quasiparticle spectral weight and highlight the importance of Cu 3d-O 2p hybridization to understand the low-energy spectral weight transfer in doped cuprates.