Zusammenfassung
The exact mapping relationship between the hybrid Ising-Heisenberg model with two-spin Heisenberg and four-spin Ising interactions and its corresponding
zero-field (symmetric) eight-vertex model, respectively, is used to study an
interesting critical behaviour of the model under investigation that satisfies
the weak universality hypothesis. In particular, it is shown that the critical exponents of the studied Ising-Heisenberg model basically depend on a ratio between the two-spin Heisenberg and four-spin Ising interactions, as well as, the strength of exchange anisotropy that allows to control a regime of the pairwise Heisenberg interaction between easy-axis and easy-plane type. In the limit of the isotropic Heisenberg coupling, an exact evidence is found for
a peculiar quantum phase transition with diverging critical exponents
$-ınfty$, $ınfty$, $ınfty$, etc.
Nutzer