Dirac-point engineering and topological phase transitions in honeycomb optical lattices
Dirac-point engineering and topological phase transitions in honeycomb optical lattices
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DOI：
10.1088/1367-2630/10/10/103027
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发表时间：
2008-10-31
影响因子：
3.3
通讯作者：
Sols, F.
中科院分区：
文献类型：
--
作者：
Wunsch, B.;Guinea, F.;Sols, F.
我们研究了六角光晶格中非相互作用费米子的电子结构和相图。在第一部分中，我们比较了蜂窝格和三角格本征谱中Dirac点的性质。数值结果补充了弱约束和强约束的分析方程。在第二部分中，我们讨论了任意最近邻跳跃的紧束缚描述下蜂窝晶格中Dirac点的相图和演化。随着跳跃之间的不对称性增加，狄拉克点彼此接近。在临界不对称时，狄拉克点合并打开能隙，从而改变本征谱的拓扑。我们分析了狄拉克点的轨迹，并研究了不同相位下的态密度。相变的比热的温度依赖性和结构因子的表现形式进行了讨论。
We study the electronic structure and the phase diagram of noninteracting fermions confined to hexagonal optical lattices. In the first part, we compare the properties of Dirac points arising in the eigenspectrum of either honeycomb or triangular lattices. Numerical results are complemented by analytical equations for weak and strong confinements. In the second part, we discuss the phase diagram and the evolution of Dirac points in honeycomb lattices applying a tight-binding description with arbitrary nearest-neighbor hoppings. With increasing asymmetry between the hoppings the Dirac points approach each other. At a critical asymmetry the Dirac points merge to open an energy gap, thus changing the topology of the eigenspectrum. We analyze the trajectory of the Dirac points and study the density of states in the different phases. Manifestations of the phase transition in the temperature dependence of the specific heat and in the structure factor are discussed.