  We analyze critical and massive SO(5) superspin regimes for correlated
electrons on a two-chain ladder. We identify fundamental low energy
excitations, which carry the quantum numbers of a free electron, and can be
probed in (inverse) photo-emission experiments. These excitations do not obey
the usual Pauli Principle, but are governed by specific forms of so-called
non-abelian exclusion statistics.

Strongly Correlated Electrons