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Charge-order on the triangular lattice: Effects of next-nearest-neighbor attraction in finite temperatures
Journal of Magnetism and Magnetic Materials ( IF 2.7 ) Pub Date : 2021-09-03 , DOI: 10.1016/j.jmmm.2021.168441
Konrad Jerzy Kapcia 1
Affiliation  

The extended Hubbard model in the atomic limit, which is equivalent to lattice S=1/2 fermionic gas, is considered on the triangular lattice. The model includes onsite Hubbard U interaction and both nearest-neighbor (W1) and next-nearest-neighbor (W2) density–density intersite interactions. The variational approach treating the U term exactly and the Wl terms in the mean-field approximation is used to investigate thermodynamics of the model and to find its finite temperature (T>0) phase diagrams (as a function of particle concentration) for W1>0 and W2<0. Two different types of charge-order (i.e., DCO and TCO phases) within 3×3 unit cells as well as the nonordered (NO) phase occur on the diagram. Moreover, several kinds of phase-separated (PS) states (NO/DCO, DCO/DCO, DCO/TCO, and TCO/TCO) are found to be stable for fixed concentration. Attractive W2<0 stabilizes PS states at T=0 and it extends the regions of their occurrence at T>0. The evolution of the diagrams with increasing of |W2|/W1 is investigated. It is found that some of the PS states are stable only at T>0. Two different critical values of |W2|/W1 are determined for the PS states, in which two ordered phases of the same type (i.e., two domains of the DCO or TCO phase) coexist.



中文翻译:

三角形晶格上的电荷顺序:有限温度下的次近邻吸引力的影响

原子极限下的扩展哈伯德模型,相当于点阵 =1/2费米子气体,被考虑在三角晶格上。该模型包括现场哈伯德 交互和最近邻(1) 和下一个最近的邻居 (2) 密度-密度点间相互作用。变分方法处理 准确的术语和 平均场近似中的项用于研究模型的热力学并找到其有限温度(>0) 相图(作为粒子浓度的函数) 1>02<0. 两种不同类型的充电顺序(即 DCO 和 TCO 阶段)3×3单元格以及无序 (NO) 相出现在图中。此外,发现几种相分离 (PS) 状态(NO/DCO、DCO/DCO、DCO/TCO 和 TCO/TCO)对于固定浓度是稳定的。吸引人的2<0 将 PS 状态稳定在 =0 并将它们的发生区域扩展到 >0. 图表随着数量的增加而演变|2|/1被调查。发现一些 PS 状态仅在>0. 两个不同的临界值|2|/1 为 PS 状态确定,其中两个相同类型的有序相(即 DCO 或 TCO 相的两个域)共存。

更新日期:2021-09-13
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