Abstract
The anisotropic XY-model in a transverse field (s = 1/2) on the
one-dimensional alternating superlattice (closed chain) is considered.
The solution of the model is obtained by introducing a generalized
Jordan-Wigner transformation which maps the system onto a
non-interacting fermion gas. The exact excitation spectrum is determined
by reducing the problem to a diagonalization of a block matrix. and it
is shown that it is numerically identical to the one obtained by using
the approximate transfer matrix method. The induced magnetization and
the susceptibility chi (approximate to approximate to) are determined as a function of the transverse field, and it is shown that, at T = 0. the
susceptibility presents multiple singularities. It is also shown, as
expected, that this critical behaviour driven by transverse field
belongs to the same universality class of the model on the alternating
chain. (C) 2001 Elsevier Science B.V. All rights reserved.
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