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 gr ound 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 he at and determine the high-temperature characteristics of the impurity. We then investigate transport properties by computing the spin and ch arge stiffnesses at zero temperature. Finally the impurity phase shift s are calculated and the existence of an impurity bound state in the h olon sector is established. (C) 1997 Elsevier Science B.V.