Evidence for strong 5d electron correlations and electron-magnon coupling in a pyrochlore, Y2Ir2O7

TL;DR

This study provides direct evidence of strong electron correlations and electron-magnon coupling in Y2Ir2O7, a pyrochlore, through high resolution photoemission spectroscopy revealing pseudogap behavior and spectral line shape evolution.

Contribution

It demonstrates the coexistence of strong 5d electron correlations and electron-magnon interactions in Y2Ir2O7, highlighting their roles in its electronic structure and magnetic properties.

Findings

Presence of a lower Hubbard band indicating strong electron correlation.

Observation of a pseudogap at the Fermi level at room temperature.

Spectral lineshape evolution below 150 K showing electron-magnon coupling.

Abstract

We report the observation of an unusual behavior of highly extended 5d electrons in Y2Ir2O7 belonging to pyrochlore family of great current interest using high resolution photoemission spectroscopy. The experimental bulk spectra reveal an intense lower Hubbard band in addition to weak intensities in the vicinity of the Fermi level, e_F. This provides a direct evidence for strong electron correlation among the 5d electrons, despite their highly extended nature. The high resolution spectrum at room temperature exhibits a pseudogap at e_F and |e - e_F|^2 dependence demonstrating the importance of electron correlation in this system. Remarkably, in the magnetically ordered phase (T < 150 K), the spectral lineshape evolves to a |e - e_F|^1.5 dependence emphasizing the dominant role of electron-magnon coupling.