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Numerical Studies of the two-leg Hubbard ladder

Zheng Weihong·J. Oitmaa·C. J. Hamer·R. J. Bursill
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Abstract

The Hubbard model on a two-leg ladder structure has been studied by a combination of series expansions at T=0 and the density-matrix renormalization group. We report results for the ground state energy $E_0$ and spin-gap $Δ_s$ at half-filling, as well as dispersion curves for one and two-hole excitations. For small $U$ both $E_0$ and $Δ_s$ show a dramatic drop near $t/t_{\perp}\sim 0.5$, which becomes more gradual for larger $U$. This represents a crossover from a "band insulator" phase to a strongly correlated spin liquid. The lowest-lying two-hole state rapidly becomes strongly bound as $t/t_{\perp}$ increases, indicating the possibility that phase separation may occur. The various features are collected in a "phase diagram" for the model.

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Zheng Weihong, J. Oitmaa, C. J. Hamer, R. J. Bursill. 2000-07-25. Numerical Studies of the two-leg Hubbard ladder. https://doi.org/10.1088/0953-8984%2F13%2F3%2F306

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