The ground state of a hole-doped t-t'-J ladder with four legs favors a striped charge distribution. Spin excitation from the striped ground state is known to exhibit incommensurate spin excitation near q=(pi,pi) forming an hourglass behavior along the leg direction (qx direction). However, an outward dispersion from the incommensurate position toward q=(0,pi) is strong in intensity, inconsistent with inelastic neutron scattering (INS) experiment. To clarify the origin of this inconsistency, we investigate the dynamical spin structure factor of n-leg t-t'-J ladder by using the dynamical density matrix renormalization group. With increasing n=4 to n=8, we find that the outward dispersion becomes weaker accompanied with weakening of stripe order in the ground state. In addition, excitation energy at q=(pi,pi) decreases with increasing n. The n=8 results are closer to INS data in hole-doped cuprates than the n=4 case. For understanding an direction dependent spin excitation reported by recent resonant inelastic x-ray scattering (RIXS) for cuprate superconductors, we also examine an 8x8 t-t'-J square lattice and obtain a consistent result with RIXS.

中文翻译：

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t-t'-J 模型中的自旋动力学：动力学密度矩阵重整化组研究

具有四个腿的空穴掺杂 t-t'-J 阶梯的基态有利于条纹电荷分布。已知来自条纹基态的自旋激发在 q=(pi,pi) 附近表现出不相称的自旋激发，形成沿腿方向（qx 方向）的沙漏行为。然而，从不公度位置向 q=(0,pi) 的向外扩散强度很强，与非弹性中子散射 (INS) 实验不一致。为了阐明这种不一致的根源，我们通过使用动态密度矩阵重整化群研究了 n-leg t-t'-J 阶梯的动态自旋结构因子。随着n=4增加到n=8，我们发现向外色散变弱，伴随着基态条纹序的减弱。此外，q=(pi,pi) 处的激发能量随着n 的增加而降低。与 n=4 的情况相比，n=8 的结果更接近于空穴掺杂铜酸盐的 INS 数据。为了理解最近的铜酸盐超导体共振非弹性 X 射线散射 (RIXS) 报告的方向相关自旋激发，我们还检查了 8x8 t-t'-J 方形晶格，并获得了与 RIXS 一致的结果。