Time-dependent and time-independent approaches to study effects of degenerate electronic states

Two types of phases are discussed in this article: (1) The topological phase as introduced by Berry [Proc. R. Sec. London, Ser. A 392, 35(1984)] and Aharonov and Anandan [Phys. Rev. Lett. 58, 1593 (1987)] and (2) the Longuet-Higgins phase [Proc. R. Sec. London, Ser. A 344, 147 (1975)]. The two types of phases have a common origin, namely the multivaluedness of the electronic adiabatic basis, a phenomenon associated with the existence of a degeneracy in configuration space. It will be shown, by studying an electronic model Hamiltonian that arises from a two-state approximation to the Mathieu equation, that the two phases differ from each other substantially, coinciding only in the adiabatic limit ripen completion of a cycle. (C) 1998 American Institute of Ph, sics. [S0021-9606(98)30440-7].