Incommensurate Phase of CuGeO3:From Solitons to Sinusoidal Modulation

An experimental and theoretical study of the field dependence of the structural modulation in the incommensurate high field phase of the spin-Peierls cuprate CuGeO3 is presented. The averaged structural order parameter is determined from magnetostriction and thermal expansion experiments in magnetic fields up to 28 T. The results are compared to density matrix renormalization group calculations using a self-consistent one-dimensional approach. The experimental and numerical data agree very well with each other and clearly show a continuous change from a solitonlike lattice close to the dimerized incommensurate transition to a sinusoidal distortion at higher fields