Comment on “Model of Fermions with Correlated Hopping (Integrable Cases)”

A Comment of the Letter by Igor N. Karnaukhov Phys. Rev. Lett. 73, 1130 (94). The authors of the Letter offer a Reply

Open t-J chain with boundary impurities

We study integrable boundary conditions for the supersymmetric t-J model of correlated electrons which arise when combining static scattering potentials with dynamical impurities carrying an internal degree of freedom. The latter differ from the bulk sites by allowing for double occupation of the local orbitals. The spectrum of the resulting Hamiltonians is obtained by means of the algebraic Bethe Ansatz.Comment: LaTeX2e, 9p

Tunneling singularities in the open Hubbard chain

We study singularities in the I-V characteristics for sequential tunneling from resonant localized levels (e.g. a quantum dot) into a one dimensional electron system described by a Hubbard model. Boundary conformal field theory together with the exact solution of the Hubbard model subject to boundary fields allows to compute the exponents describing the singularity arising when the energy of the local level is tuned through the Fermi energy of the wire as a function of electron density and magnetic field. For boundary potentials with bound states a sequence of such singularities can be observed.Comment: LaTeX2e, 16 pp. incl. 9 figure

Exact solution of a t-J chain with impurity

We study the effects of an integrable impurity in a periodic t-J chain. The impurity couples to both spin and charge degrees of freedom and has the interesting feature that the interaction with the bulk can be varied continuously without losing integrability. We first consider ground state properties close to half-filling in the presence of a small bulk magnetic field. We calculate the impurity contributions to the (zero temperature) susceptibilities and the low temperature specific heat and determine the high-temperature characteristics of the impurity. We then investigate transport properties by computing the spin and charge stiffnesses at zero temperature. Finally the impurity phase--shifts are calculated and the existence of an impurity bound state in the holon sector is established.Comment: 33 pages Latex, figures include

Spectrum of boundary states in the open Hubbard chain

We use the Bethe Ansatz solution for the one dimensional Hubbard model with open boundary conditions and applied boundary fields to study the spectrum of bound states at the boundary. Depending on the strength of the boundary potentials one finds that the true ground state contains a single charge or, for boundary potentials comparable to the Hubbard interaction, a pair of electrons in a bound state. If these are left unoccupied one finds holon and spinon bound states. We compute the finite size corrections to the low lying energies in this system and use the predictions of boundary conformal field theory to study the exponents related to the orthogonality catastrophe.Comment: LaTeX + epsf,amssymb macros, 14 pp. incl. figure

Integrable impurity in the supersymmetric t-J model

An impurity coupling to both spin and charge degrees of freedom is added to a periodic t-J chain such that its interaction with the bulk can be varied continuously without losing integrability. Ground state properties, impurity contributions to the susceptibilities and low temperature specific heat are studied as well as transport properties. The impurity phase--shifts are calculated to establish the existence of an impurity bound state in the holon sector.Comment: RevTeX+epsf macros, 4pp. including 4 figure