Anomalous doping evolution of nodal dispersion revealed by in-situ ARPES on continuously doped cuprates

TL;DR

This study uses in-situ ARPES to analyze how the nodal dispersion in a high-temperature superconductor evolves with doping, revealing three segments with distinct velocities and potential electron fractionalization effects.

Contribution

It uncovers the doping-dependent evolution of nodal dispersion segments and suggests electron fractionalization as a cause for anomalous dispersion in cuprates.

Findings

Nodal dispersion has three segments separated by two kinks.

High-energy segment velocity increases as doping decreases.

Electron fractionalization may explain anomalous dispersion.

Abstract

We study the systematic doping evolution of nodal dispersions by in-situ angle-resolved photoemission spectroscopy on the continuously doped surface of a high-temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$. We reveal that the nodal dispersion has three segments separated by two kinks, located at ~10 meV and roughly 70 meV, respectively. The three segments have different band velocities and different doping dependence. In particular, the velocity of the high-energy segment increases monotonically as the doping level decreases and can even surpass the bare band velocity. We propose that electron fractionalization is a possible cause for this anomalous nodal dispersion and may even play a key role in the understanding of exotic properties of cuprates.