They aren't excitations of individual electrons, but of the system as a whole. I'd assume they're some sort of quasi-particle, though this isn't really my fiel

They aren't excitations of individual electrons, but of the system as a whole. I'd assume they're some sort of quasi-particle, though this isn't really my field. http://en.wikipedia.org/wiki/Quasiparticle http://en.wikipedia.org/wiki/Quasiparticle http://en.wikipedia.org/wiki/Spin_liquid#Excitations http://en.wikipedia.org/wiki/Spin_liquid#Excitations