Functional Bethe ansatz methods for superspin chains: treatment of boundary fields and transport problems

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In this project we plan to study the effect of boundary conditions which break particle number conservation on the low-energy spectrum of integrable superspin chains. Such models are not accessible to the well established (graded) quantum inverse scattering method. In particular the algebraic Bethe ansatz cannot be used to solve the spectral problem due to the absence of a simple reference state. The focus of our proposal is on a system of interacting spinless fermions, the so-called small polaron model. Adding non-diagonal boundary fields to this model allows to investigate basic questions related to certain transport properties of this and related models. Using functional Bethe ansatz methods developed before for integrable spin-1/2 chains we shall determine the ground state and low energy excitations and compute the current induced by the boundary terms. First steps will be taken towards the construction and solution of similar integrable models for particles with additional degrees of freedom, e.g. spin.