  In a spontaneously dimerized quantum antiferromagnet, spin-1/2 excitations
(spinons) are confined in pairs by strings akin to those confining quarks in
non-abelian gauge theories. The system has multiple degenerate ground states
(vacua) and domain walls between regions of different vacua. For two vacua, we
demonstrate that spinons on a domain wall are liberated, in a mechanism
strikingly similar to domain-wall deconfinement of quarks in variants of
quantum chromodynamics. This observation not only establishes a novel
phenomenon in quantum magnetism, but also provides a new direct link between
particle physics and condensed-matter physics. The analogy opens doors to
improving our understanding of particle confinement and deconfinement by
computational and experimental studies in quantum magnetism.
