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arXiv · 0810.2539

Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths

S. Miyashita·Y. Yamashita·K. Yonemitsu·A. Koga·N. Kawakami
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Abstract

We investigate the ground-state properties of the one-dimensional two-band Hubbard model with different bandwidths. The density-matrix renormalization group method is applied to calculate the averaged electron occupancies $n$ as a function of the chemical potential $\mu$. Both at quarter and half fillings, "charge plateaux" appear in the $n$-$\mu$ plot, where $d\mu/dn$ diverges and the Mott insulating states are realized. To see how the orbital polarization in the one-quarter charge plateau develops, we apply the second-order perturbation theory from the strong-coupling limit at quarter filling. The resultant Kugel-Khomskii spin-orbital model includes a $magnetic$ field coupled to orbital pseudo-spins. This field originates from the discrepancy between the two bandwidths and leads to a finite orbital pseudo-spin magnetization.

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S. Miyashita, Y. Yamashita, K. Yonemitsu, A. Koga, N. Kawakami. 2008-10-14. Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths. https://doi.org/10.1088/1742-6596/150/4/042128

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