Physical review. B, Condensed matter
Exact time-dependent propagation of vacancy motion in thet-Jlimit of the two-dimensional Hubbard Hamiltonian
Qing Zhang, K. Birgitta Whaley
Abstract
A technique to perform real-time quantum propagation of many-particle systems on finite lattices is presented and applied to the motion of a single hole in the Heisenberg and Ising magnets (t-J and t-${\mathit{J}}_{\mathit{z}}$ models) for finite two-dimensional lattices of sizes 3\ifmmode\times\else\texttimes\fi{}3 and 4\ifmmode\times\else\texttimes\fi{}4. Use of Trotter's formula together with a checkerboard decomposition allows a direct real-time calculation of the many-fermion dynamics to be made for asymptotically long times. Starting from localized initial states, the hole-density distribution in the single-hole system is evaluated as a function of time. We find statistical behavior already appears in the 4\ifmmode\times\else\texttimes\fi{}4 lattice due to the large Hilbert space of the fermion background (\ensuremath{\approxeq}${10}^{5}$ states). For J\ensuremath{\ll}t, the hole appears to move almost incoherently in both models, with small quantum fluctuations. For larger values of the spin coupling J, the t-${\mathit{J}}_{\mathit{z}}$ model shows a strong tendency to localize, while incorporation of the Heisenberg spin-flip term removes this feature and introduces an increasing component of low-frequency coherent motion for larger J.