Incoherent strange metal sharply bounded by the pseudogap critical doping in Bi2212*

In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest Tc is found to be very different and called the “strange metal”. In this talk, I will present a comprehensive angle-resolved photoemission study of its spectral function in Bi2212 [1]. With increasing doping across a temperature-independent critical value pc ~ 0.19, we observe a dramatic change near the Brillouin zone boundary where the strange metal characterized by incoherent spectral function abruptly reconstructs into a more conventional metal with quasiparticle-like excitations. Furthermore, above the temperature scale of superconducting fluctuations, we find that the pseudogap—the anomalous suppression of low-energy spectral intensity with decreasing temperature—also sharply collapses at the very same pc. These observations suggest that the incoherent strange metal is a prerequisite for the pseudogap and challenge presumptions associating the pseudogap with a quantum critical point.

[1] Chen, Hashimoto et al., Science 366, 1099 (2019)