Hidden structure in the spectra of strongly correlated electrons in 1d

TL;DR

This paper uncovers a hidden structure in the spectra of one-dimensional strongly correlated electron systems, revealing an anomalous gapped excitation branch that can switch between spin and charge sectors without altering the ground state.

Contribution

It provides a classification of the energy spectrum in Bethe ansatz solvable models, highlighting the behavior of anomalous excitation branches and their sector-switching properties.

Findings

Identification of a gapped anomalous excitation branch

Classification of spectral structures in solvable models

Demonstration of sector-switching behavior of excitations

Abstract

We identify a structure in the spectra of 1d lattice models of interacting electrons, characterised by an anomalous gapped branch of elementary excitations. Focusing on a family of Bethe ansatz solvable models, where all excitations are stable against decay, we make a four-way classification of the energy spectrum along with a model belonging to each class. We find in particular that the anomalous excitation branch may switch between the spin and charge symmetry sectors without a change in the ground state. Instead it changes its nature by becoming inaccessible to the ground state.