Multicritical Points in Incommensurate Systems

Abstract

Since Hornreich et al¹ introduced the concept of a Lifshitz point — i. e. a triple point in the Pressure-Temperature phase diagram, separating two lines of continuous transitions to ferromagnetic and helicoidal phases — a large number of theoretical studies have discussed the symmetry and critical properties of this multicritical point^2–5. Experimental evidence of a Lifshitz point was also claimed for a large variety of compounds undergoing magnetic⁶, structural⁷, liquid crystal⁸ , as well as surface phase transitions⁹. However, as noted by Aslanyan and Levanyuk¹⁰ the Lifshitz point considered in Ref. 1 corresponds to a physical situation which is not the more likely to occur. Accordingly, these authors defined three other types of Lifshitz points¹⁰