Commensurate-incommensurate transition: on the coupling between phase solitons and strain

A Ginzburg-Landau model for the commensurate-incommensurate phase transition with coupling between solitons and elastic distortions in one dimension is treated. The model was recently studied by other authors but only incomplete solutions were given. Depending on the relative magnitude of coupling constants the authors find two regions of first- and second-order transitions, separated by a line of tricritical points. The previous results by Bruce, Cowley and Murray (1978) and by Bak and Timonen (1978) are found as limits for stiff and soft elastic distortions.