Abstract We use cluster density matrix embedding theory (CDMET) to calculate the excited states for quantum spin systems. The bath states are a set of block-product states and optimized by the variational method. By considering the symmetry in the form of penalty function, the degeneracy of excited eigenstates can be reduced. We prove the accuracy of our method by obtaining different excited states of square Heisenberg model. The ground state is nondegenerate state with gapless excitation in the ordered phase or degenerate state with an excitation energy gap in disordered phase. This is consistent with some previous results and supports the Lieb–Schultz–Mattis theorem. Moreover, we find some interesting behaviors of excited states for different coupling coefficient and different target energy under different symmetries.

中文翻译：

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自旋系统激发态密度矩阵嵌入理论

摘要 我们使用簇密度矩阵嵌入理论（CDMET）来计算量子自旋系统的激发态。浴状态是一组块积状态并通过变分方法优化。通过考虑惩罚函数形式的对称性，可以减少激发本征态的简并性。我们通过获得方形​​海森堡模型的不同激发态来证明我们方法的准确性。基态是在有序相中具有无间隙激发的非简并态或在无序相中具有激发能隙的简并态。这与之前的一些结果一致并支持 Lieb-Schultz-Mattis 定理。此外，我们发现了不同对称性下不同耦合系数和不同目标能量的激发态的一些有趣行为。