  There are several two dimensional quantum field theory models which are
equipped with different vacuum states. For example the Sine-Gordon- and the
$\phi^4_2$-model. It is known that in these models there are also states,
called soliton- or kink-states, which interpolate different vacua. We consider
the following question: Which are the properties a pair of vacuum sates must
have, such that an interpolating kink-state can be constructed? Since we are
interested in structural aspects and not in specific details of a given model,
we are going to discuss this question in the framework of algebraic quantum
field theory which includes, for example, the $P(\phi)_2$-models. We have shown
that for a large class of vacuum states, including the vacua of the
$P(\phi)_2$-models, there is a natural way to construct an interpolating
kink-state.
