The field-induced soliton phase of CuGeO3

The quasi-1D S = 1/2 antiferromagnet CuGeO3 undergoes a spin-Peierls transition to a dimerised singlet quantum ground state, with S = 1 carrying pairs of domain walls as elementary excitations. Applying a large magnetic field, the domain walls-solitons-can be condensed into the ground state, forming a static incommensurate soliton lattice, which has been investigated by neutron scattering. The static soliton structure was found to be in good accordance to field theoretical and numerical calculations, while a low energy incommensurate mode is interpreted as a gapped phason. We anticipate that theoretical description of this and higher energy excitations will provide general insight to the effect of structural fluctuations on correlated electron systems.