ELECTRON-MOMENTUM DISTRIBUTION AND SPECTRAL-FUNCTION FOR 2 HOLES IN FINITE-CLUSTER T-J MODELS

We calculated the momentum distribution and one-particle spectral function for the ground state of two holes in a finite-cluster t-J model in the framework of the string picture. Previous numerical results for these quantities could be reproduced at least qualitatively. Our interpretation of these data, however, supports a rigid-band approximation starting from the single-hole case rather than a nearest-neighbor hopping band and large Fermi surface. We argue that in order to interpret the finite-cluster data properly, it is crucial to take into account the well-established fact that the ground state of two holes in a finite cluster is a bound state with nontrivial symmetry.