Aspects of the ground state of the $U=\infty$ Hubbard ladder

Masanori Kohno

doi:10.1103/PhysRevB.56.15015

paper

Aspects of the ground state of the $U = \infty$ Hubbard ladder

arXiv:cond-mat/9709170 · doi:10.1103/PhysRevB.56.15015

Abstract

We consider two aspects of the ground state of the $U = \infty$ Hubbard ladder: ferromagnetism and the metal-insulator transition at quarter-filling. First, we present rigorous results for the $U = \infty$ Hubbard ladder in the limit of the large inter-chain hopping ( $t_{⊥} / t \to \infty$ ). In this limit, the total spin $S$ of the ground state is shown to be zero for the electron density $n \leq 0.5$ and its maximum ( $S = S_{ma x}$ ) for $n > 0.5$ . The charge gap at quarter-filling is $2 t_{⊥}$ . We extend these results to finite $t_{⊥} / t$ by means of the density-matrix renormalization group method. We estimate the phase boundaries with respect to spontaneous magnetization and the charge gap at quarter-filling for finite $t_{⊥} / t$ . Applying the extended Aharonov-Bohm method, we give numerical evidence that the critical ratio $t_{⊥} / t$ , above which the charge gap opens, is less than 0.001. Ferromagnetism in the t-J ladder is briefly discussed.

24 pages, RevTex, 11 figures, to appear in Phys.Rev.B

Aspects of the ground state of the U=∞ Hubbard ladder

Abstract

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Aspects of the ground state of the $U = \infty$ Hubbard ladder