Ferrotoroidic Moment as a Quantum Geometric Phase

C. D. BATISTA, G. ORTIZ, AND A. A. ALIGIA

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Lugar: New York; Año: 2008 vol. 101 p. 772031 - 772034

0031-9007

We present a geometric characterization of the ferrotoroidic moment${oldsymbol au}$ in terms of a set of  Abelian Berry phases.   Wealso introduce a fundamental complex quantity, $z_{mu u}$,  whichallows to discriminate between systems with or without ferrotoroidicspin moment,  and is derived from  the tensor $T_{mu u}= 2 sum_jr^{mu}_j S^{ u}_j$. This geometric framework also provides a natural computational approach for both density functional theory and many-body methods.