Dual origin in the temperature dependence of the coupling parameter for the strange metal state in heavily overdoped cuprate superconductor

Abstract

The real and imaginary parts of the self-energy in the wide energy range have been evaluated from high-resolution angle-resolved photoemission spectroscopy (ARPES) spectra of a heavily overdoped single-layer cuprate superconductor (Bi,Pb)2Sr2CuO6+δ in the normal state. The real part of the self-energy has the zero-point crossing at −0.6 eV, where the lifetime broadening takes maximum and the ARPES spectral intensity is significantly suppressed forming a high-energy anomaly (HEA). The self-energy part responsible for the HEA is almost temperature independent and the coupling parameter is λHEA∼1 at 300 K, indicating strongly correlated nature of the strange metal state. Meanwhile, the self-energy part responsible for the low-energy kink (LEK) near the Fermi level shows significant temperature dependence: it is λLEK∼0.1 at 300 K but enhances steeply below ∼150K up to λLEK∼0.8, leading to the total coupling strength of λtot=λHEA+λLEK=1.8 at 20 K. The temperature-dependent enhancement cannot be explained by the electron-phonon interaction with a fixed magnitude of the Eliashberg function, which suggests an unexplored mechanism that enhances the coupling parameter at lower temperatures. Our results clearly indicate distinct energy scales in the self-energy, providing insight into the strange metal state as well as the temperature-dependent interplay of many-body interactions.

Source-reported materials — not catalogue approval

Similar papers