Fractional charges in pyrochlore lattices

TL;DR

This paper explores fractional charge excitations in a pyrochlore lattice with strong electron interactions, revealing that added electrons can fractionalize into charge e/2 excitations linked by a spin chain.

Contribution

It demonstrates the existence of fractional charges in pyrochlore lattices under strong repulsions, connecting fractionalization to ground state degeneracy and spin-charge separation.

Findings

Existence of fractional charge (+/-) e/2 excitations.

Fractional charges emerge from ground state degeneracy.

Added electrons decay into two e/2 charges connected by a spin chain.

Abstract

A pyrochlore lattice is considered where the average electron number of electrons per site is half--integer, concentrating on the case of exactly half an electron per site. Strong on-site repulsions are assumed, so that all sites are either empty or singly occupied. Where there are in addition strong nearest--neighbour repulsions, a tetrahedron rule comes into effect, as previously suggested for magnetite. We show that in this case, there exist excitations with fractional charge (+/-) e/2. These are intimately connected with the high degeneracy of the ground state in the absence of kinetic energy terms. When an additional electron is inserted into the system, it decays into two point like excitations with charge -e/2, connected by a Heisenberg spin chain which carries the electron's spin.