Normal State Spectral Lineshapes of Nodal Quasiparticles in Single Layer Bi2201 Superconductor

TL;DR

This study reveals a double peak spectral feature and strong quasiparticle-lattice coupling in the normal state of Bi2201 superconductor, extending understanding of its electronic interactions well above the critical temperature.

Contribution

First experimental evidence of a double peak and spectral dip in the normal state of Bi2201, indicating strong quasiparticle-boson coupling and mass renormalization effects.

Findings

Double peak structure persists up to ten times the critical temperature.

Observation of a kink in quasiparticle dispersion indicating mass renormalization.

Enhanced quasiparticle lifetime in the normal state.

Abstract

A detailed study of the normal state photoemission lineshapes and quasiparticle dispersion for the single layer Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ (Bi2201) superconductor is presented. We report the first experimental evidence of a double peak structure and a dip of spectral intensity in the energy distribution curves (EDCs) along the nodal direction. The double peak structure is well identified in the normal state, up to ten times the critical temperature. As a result of the same self-energy effect, a strong mass renormalization of the quasiparticle dispersion, i.e. kink, and an increase of the quasiparticle lifetime in the normal state are also observed. Our results provide unambiguous evidence on the existence of bosonic excitation in the normal state, and support a picture where nodal quasiparticles are strongly coupled to the lattice.