Ground state of 1D Hubbard model: Is Lieb and Wu solution incomplete?

In their 1968 paper "ABSENCE OF MOTT TRANSITION IN AN EXACT SOLUTION OF SHORT-RANGE 1-BAND MODEL IN 1 DIMENSION", PHYS REV LETT 20: (25) 1445, Lieb and Wu solved ground state of 1d Hubbard model by using Bethe Ansatz. However, this solution is not complete. In our paper  "Bound electron pairs in strongly correlated models of high temperature superconductivity", with I.O. Kulik, we showed that there exist more solutions to 1d Hubbard model than the ones found by Lieb and Wu method alone. We also showed that these new ground state eigenstates may lead to superconductivity in 1d Hubbard model with a repulsive onsite interaction between fermions. However, it is important to note that, those findings do not change the main conclusion of 1968 paper, that is there is still no Mott transition in 1d Hubbard model.

The contraction model or the occupation dependent hopping model of high temperature superconductivity.

Cooper instability in occupation dependent model.

Effect of degeneracy on ground state of ultrasmall superconducting metals.
 

Recent publications

H. Boyaci and Igor O. Kulik, "Bound electron pairs in strongly correlated models of high temperature superconductivity", Low Temperature Physics 24, 239 (1998).

H. Boyaci and I. O. Kulik, "Cooper instability in the occupation dependent hopping Hamiltonians", Low Temperature Physics 25, 625 (1999). Also in cond-mat/9904118

H. Boyaci, Z. Gedik, and I. O. Kulik, "Superconductivity in Mesoscopic Metal Particles", Journal of Superconductivity: Incorporating Novel Magnetism 13, 1031 (2000). Also in cond-mat/9909386

H. Boyaci, Z. Gedik, and I. O. Kulik, "Superconductivity in ultrasmall grains", in "Quantum mesoscopic phenomena and mesoscopic devices in microelecteronics. Proceedings of the NATO Advanced Study Institute, Ankara, Turkey, 13-25 June 1999," Edited by Igor O. Kulik and Recai Ellialtioglu, Kluwer Academic Publishers, Dordrecht (2000).

I. O. Kulik, H. Boyaci, and Z. Gedik, "Parity Effect in Mesoscopic and Nanoscopic Superconducting Particles", Physica C 352, 46 (2001). Also in cond-mat/0006003