Gaps in the Heisenberg-Ising model.
Gaps in the Heisenberg-Ising model.
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海森堡-伊辛模型中的缺陷。
DOI：
10.1103/physrevb.52.1656
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Sutherland
中科院分区：
文献类型：
--
作者：
Römer;Èckle;Sutherland
我们报告的关键海森堡-伊辛链在动量$\pi$的基态关闭的差距。对于半填充，差距在各向异性的特殊值$\Delta= \cos（\pi/Q）$，$Q$ integer处闭合。我们解释了这种行为的帮助下的贝特Anastomy和显示，差距规模作为一个权力的系统大小的可变指数取决于$\Delta$。我们使用有限大小的分析来计算这个指数的临界区域，补充微扰理论在$\Delta\sim 0$。对于合理的$1/r$的填充，差距示出为关闭的{\em all}值的$\Delta$和相应的扰动展开在$\Delta$显示了显着的各种图的取消。
We report on the closing of gaps in the ground state of the critical Heisenberg-Ising chain at momentum $\pi$. For half-filling, the gap closes at special values of the anisotropy $\Delta= \cos(\pi/Q)$, $Q$ integer. We explain this behavior with the help of the Bethe Ansatz and show that the gap scales as a power of the system size with variable exponent depending on $\Delta$. We use a finite-size analysis to calculate this exponent in the critical region, supplemented by perturbation theory at $\Delta\sim 0$. For rational $1/r$ fillings, the gap is shown to be closed for {\em all} values of $\Delta$ and the corresponding perturbation expansion in $\Delta$ shows a remarkable cancellation of various diagrams.