A New Type of Incommensurate Phase Transition Caused by Parabolic Splitting of Degenerate Modes

作者：Ishibashi Yoshihiro^*; Iwata Makoto

来源：Journal of the Physical Society of Japan, 2013, 82(4): 044703.

DOI：10.7566/JPSJ.82.044703

• MOPT-lattice
• saddlelike dispersion relation
• saddle point
• parabolic splitting
• degenerate modes
• incommensurate phase transition
• commensurate phase

On the basis of the model of the minimal lattice with orthogonal partial translation (MOPT) lattice, it is shown that, around a special point at the Brillouin zone boundary, a saddlelike dispersion relation appears and the parabolic splitting of degenerate modes takes place. A new type of incommensurate phase is stabilized by the freezing of the soft mode belonging to the lower branch induced by the parabolic splitting. A simple model theory of the incommensurate phase transition of this type is proposed, which easily reproduces one of the most remarkable features showing that the macroscopic symmetry changes in the incommensurate phase transition.

• 出版日期2013-4