Charge-order on the triangular lattice: Effects of next-nearest-neighbor attraction in finite temperatures

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:541

Article

Kapcia, Konrad Jerzy¹ 

[1] Adam Mickiewicz Univ, Fac Phys, Ulica Uniwersytetu Poznanskiego 2, PL-61614 Poznan, Poland

关键词: Charge order;    Triangular lattice;    Fermionic lattice gas;    Longer-range interactions;    Extended Hubbard model;    Atomic limit;   

DOI  :  10.1016/j.jmmm.2021.168441

来源: Elsevier

【 摘 要 】

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.. interaction and both nearest-neighbor (W-1) and next-nearest-neighbor (W-2) density-density intersite interactions. The variational approach treating the.. term exactly and the W-1 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 W-1 > 0 and W-2 < 0. Two different types of charge-order (i.e., DCO and TCO phases) within root 3 x root 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 W-2 < 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 vertical bar W-2 vertical bar/W-1 is investigated. It is found that some of the PS states are stable only at T > 0. Two different critical values of vertical bar W-2 vertical bar/W-1 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.

【 授权许可】

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