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arXiv · 2210.03276

Excited States beyond Mott Gap in Half-Filled-Band Hubbard Model

Hisatoshi Yokoyama·Kenji Kobayashi·Tsutomu Watanabe·Masao Ogata
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Abstract

In connection with recent experiments on excitation in which Mott insulators change to conductors, we study the properties of excited states beyond the Mott gap as quasi-stationary states for a two-dimensional Hubbard (t-t'-U) model at half filling. A variational Monte Carlo method is used with trial wave functions for paramagnetic or normal (PM), superconducting with dx2-y2-wave (d-SC), isotropic s-wave, and extended s-wave symmetries, and antiferromagnetic (AF) states. The excited states are generated by imposing a minimum number of doubly occupied sites (doublons) D_L on the lowest-energy states. For U>W (W: band width), d_L=D_L/Ns (Ns: number of sites) corresponds to the excitation intensity. It is found that the AF state is the most stable among the states we treated for d_L<0.14 and insulating. The PM and d-SC states become conductive over a threshold d_Lc, and the conduction is caused by unbound doublons and holons (empty sites). The PM state arises for d_L>0.14, but the d-SC state is always hidden by the AF state. The s-wave-type superconducting states are not stabilized for any parameter set.

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Hisatoshi Yokoyama, Kenji Kobayashi, Tsutomu Watanabe, Masao Ogata. 2022-10-07. Excited States beyond Mott Gap in Half-Filled-Band Hubbard Model. https://doi.org/10.7566/jpsj.91.124705

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