An ARPES Study of the Electronic Structure of the Quantum Spin Liquid EtMe3Sb[Pd(dmit)2]2

TL;DR

This study uses ARPES to investigate the electronic structure of the quantum spin liquid EtMe3Sb[Pd(dmit)2]2, revealing bands consistent with isolated dimers, a small Mott gap, and polaronic spectral features, highlighting strong electron-boson interactions.

Contribution

First ARPES analysis of EtMe3Sb[Pd(dmit)2]2 revealing detailed electronic structure and interactions in a quantum spin liquid.

Findings

Identified several flat bands matching dimer energy levels.

Detected a ~50 meV Mott gap between the lower Hubbard band and chemical potential.

Observed polaronic spectral features with broad linewidths.

Abstract

The electronic structure of a quantum spin liquid compound, EtMe3Sb[Pd(dmit)2]2, has been studied with angle-resolved photoemission spectroscopy, together with two other Pd(dmit)2 salts in the valence bond solid or antiferromagnetic state. We have resolved several bands that have negligible dispersions and fit well to the calculated energy levels of an isolated [Pd(dmit)2]2 dimer. EtMe3Sb[Pd(dmit)2]2 being a Mott insulator, its lower Hubbard band is identified, and there is a small gap of ~ 50 meV between this band and the chemical potential. Moreover, the spectral features exhibit polaronic behavior with anomalously broad linewidth. Compared with existing theories, our results suggest that strong electron-boson interactions, together with smaller hopping and on-site Coulomb interaction terms have to be considered for a realistic modeling of the organic quantum spin liquid systems like the Pd(dmit)2 salt.