Landau theory of the charge-density-wave state in tantalum diselenide under pressure

It has recently been observed by McWhan and co-workers that the commensurate charge density wave in $2H-\mathrm{T}\mathrm{a}{\mathrm{Se}}_2$ can be suppressed by a pressure $P\approx 2$ GPa only to reappear again at higher pressures. This behavior can be explained if the energy to introduce a discommensuration in the commensurate phase goes through a minimum. This can happen if the interlayer coupling causes the intralayer phase to move from one minimum to another. A quantitative discrepancy remains and it is suggested that this may be due to impurity pinning effects on the discommensurations.