Lattice and magnetic instabilities near the neutral-ionic phase transition of the one-dimensional extended Hubbard model with alternating potentials in the thermodynamic limit
Lattice and magnetic instabilities near the neutral-ionic phase transition of the one-dimensional extended Hubbard model with alternating potentials in the thermodynamic limit
复制标题
热力学极限内具有交变电势的一维扩展哈伯德模型中性离子相变附近的晶格和磁不稳定性
DOI：
10.1103/physrevb.65.205105
复制
发表时间：
2002
影响因子：
3.7
通讯作者：
K. Yonemitsu
中科院分区：
文献类型：
--
作者：
K. Yonemitsu
在半填充交变电位的一维扩展Hubbard模型中，研究了二聚化引起的传递积分变化对中性离子相变的影响。采用有限温度密度-矩阵重整化-群方法处理热力学极限。在离子相中，自由能增益与δ 4 / 3成正比，δ为低温下在相边界附近的二聚化程度。在中性相中，在远离相边界的小传递积分处，自由能增益是二次型的，但在靠近相边界处，自由能增益是非线性增强的。大的转移积分使增益比δ 2快，因此它们有利于二聚化。中性相的二聚化增加了离子性，降低了自旋激发能。这些晶格效应与交错磁场的效应相反。讨论了这些结果与最近观察到的CIMePD-DMeDCNQI中性相二聚化的相关性。
The effects of dimerization causing the alternation of transfer integrals on the neutral-ionic phase transition are studied in the one-dimensional extended Hubbard model with alternating potentials at half filling. The finite-temperature density-matrix renormalization-group method is used to treat the thermodynamic limit. In the ionic phase, the free-energy gain is proportional to δ 4 / 3 with δ being the degree of dimerization even near the phase boundary at low temperatures. In the neutral phase, the free-energy gain is quadratic for small transfer integral far from the phase boundary, but it is nonlinearly enhanced near the boundary. Large transfer integrals make the gain faster than δ 2 , so that they facilitate dimerization. The dimerization in the neutral phase increases the ionicity and lowers the spin excitation energies. These lattice effects are in contrast to the effects of a staggered magnetic field. The relevance of these results to recently observed dimerization in the neutral phase of CIMePD-DMeDCNQI is discussed.