Three relaxation processes from an electric-field-induced polar structure in a columnar liquid crystalline urea derivative

We have studied the polarization relaxation process after removing an applied electric field in the columnar hexagonal phase of N,N^'-bis(3,4,5-trihexadecyloxyphenyl)urea by means of second-harmonic generation (SHG), switching current, and texture observation. Transient SHG and current associated by sudden field change show polarization switching associated with a molecular reorientation of about a few ms depending on the field strength. Furthermore, the texture observation reveals a column undulation process during 100.3em0exs0.3em0exto0.3em0ex10.3em0exmin. The size of the polar domains was estimated to be 1600.3em0exmolecules by analyzing the field dependence of the SHG signal intensity on the basis of an Ising model.