LOW-TEMPERATURE SPECIFIC-HEAT OF THE DEGENERATE SUPERSYMMETRIC T-J MODEL IN ONE-DIMENSION

We consider the one-dimensional SU(N) invariant t-J model, which consi sts of electrons with N spin components on a lattice with nearest-neig hbor hopping t constrained by the excluded multiple occupancy of the s ites and spin-exchange J between neighboring lattice sites. The model is integrable and has been diagonalized in terms of nested Bethe ansat ze at the supersymmetric point t=J. The low-T specific heat is proport ional to T. The gamma-coefficient is extracted from the thermodynamic Bethe-ansatz equations and is expressed in terms of the spin wave velo cities and the group velocity of the charges for arbitrary N, band fil ling, and splitting of the levels (magnetic and crystalline fields). O ur results contain the following special cases: (i) For N=2 the tradit ional spin-1/2, supersymmetric t-J model, (ii) for exactly one electro n per site the SU(N)-Heisenberg chain, and (iii) for N=4 the two-band supersymmetric t-J model with crystalline field splitting. (C) 1996 Am erican Institute of Physics.