Crossover from coherent quasiparticles to incoherent hole carriers in underdoped cuprates

Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi  ; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

In underdoped cuprates, only a portion of the Fermi surface survives as Fermi arcs due to pseudogap opening. In hole-doped LaCuO, we have deduced the "coherence temperature" of quasiparticles on the Fermi arc above which the broadened leading edge position in angle-integrated photoemission spectra is shifted away from the Fermi level and the quasiparticle concept starts to lose its meaning. is found to rapidly increase with hole doping, an opposite behavior to the pseudogap temperature . The superconducting dome is thus located below both and , indicating that the superconductivity emerges out of the coherent Fermionic quasiparticles on the Fermi arc. remains small in the underdoped region, indicating that incoherent charge carriers originating from the Fermi arc are responsible for the apparently metallic transport at high temperatures.