arXiv:cond-mat/9712134 · Physical review. B, Condensed matter
Density-matrix renormalization-group study of the spin gap in a one-dimensional Hubbard model: Effect of the distant transfer and exchange coupling
Ryotaro Arita, Kazuhiko Kuroki, Hideo Aoki, Michele Fabrizio
Abstract
The spin gap of a one-dimensional repulsive Hubbard model is numerically calculated with the density-matrix renormalization group, with a special emphasis on the effect of a next-nearest-neighbor hopping ${(t}^{\ensuremath{'}})$ and the nearest-neighbor ferromagnetic exchange $(J)$ interaction. At half filling, a significant spin gap opens if $|{t}^{\ensuremath{'}}|\ensuremath{\simeq}|t|$ and $J=0$, in agreement with the weak-coupling theory, while the gap is strongly suppressed by the introduction of $J$. On the other hand, the quarter-filled system has very small spin gaps regardless of the values of ${t}^{\ensuremath{'}}$ and $J$. Implications for the ${\mathrm{CuO}}_{2}$ chain in ${\mathrm{Sr}}_{14}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ and related materials are discussed.