A universal high energy anomaly in angle resolved photoemission spectra of high temperature superconductors - possible evidence of spinon and holon branches

TL;DR

This study reports a universal high energy anomaly in the spectral function of high temperature superconductors, revealing dispersion anomalies at specific energy scales that suggest the separation of quasiparticles into spinon and holon branches.

Contribution

The paper provides experimental evidence of a high energy anomaly in ARPES spectra across different cuprate families, indicating a possible spin-charge separation in high T_c superconductors.

Findings

Identification of two high energy scales E_1 and E_2 with dispersion anomalies.

Observation of dispersion splitting into two branches above E_1.

Re-emergence of band-like dispersion above E_2.

Abstract

A universal high energy anomaly in the single particle spectral function is reported in three different families of high temperature superconductors by using angle-resolved photoemission spectroscopy. As we follow the dispersing peak of the spectral function from the Fermi energy to the valence band complex, we find dispersion anomalies marked by two distinctive high energy scales, E_1=~ 0.38 eV and E_2=~0.8 eV. E_1 marks the energy above which the dispersion splits into two branches. One is a continuation of the near parabolic dispersion, albeit with reduced spectral weight, and reaches the bottom of the band at the gamma point at ~0.5 eV. The other is given by a peak in the momentum space, nearly independent of energy between E_1 and E_2. Above E_2, a band-like dispersion re-emerges. We conjecture that these two energies mark the disintegration of the low energy quasiparticles into a spinon and holon branch in the high T_c cuprates.