论文标题
Lifshitz附近的De Haas-Van Alphen振荡从两个电子口袋过渡到二维Dirac Fermion Systems的一个电子口袋
De Haas-van Alphen oscillations near the Lifshitz transition from two electron pockets to one electron pocket in the two-dimensional Dirac fermion systems
论文作者
论文摘要
我们从理论上研究了系统中的De Haas-Van Alphen（DHVA）振荡，并通过电子掺杂改变了费米表面（Lifshitz Transition）的拓扑。在压力下，我们采用$α$ - （bedt-ttf）$ _ 2 $ i $ _3 $的二维紧密绑定模型，在压力下，在第一个布里远区有两个狄拉克点。当该系统略微掺杂时，存在两个封闭的费米表面，具有相同的区域，而DHVA振荡分别在固定电子填充（$ν$）或固定的化学势（$μ$）的情况下，将变为锯齿状图案或锯齿状图案，分别相对于磁场。通过增加兴奋剂，系统接近Lifshitz的过渡，其中两个封闭的费米表面彼此紧密。然后，我们发现DHVA振荡的模式发生了变化。磁化的跳跃出现在基本周期的中心，在固定电子填充的情况下，其幅度增加，而跳跃分为一对跳跃，在固定化学势的情况下，其分离变得很大。这是由于在兰道水平上取消了双重变性。由于这种举重在带有两个狄拉克点的二维迪拉克费米式系统中可以看到，因此本研究中获得的结果不仅可以应用于$α$ - （bedtt-ttf）$ _ 2 $ _ 2 $ _ 2 $ i $ _3 $，还有其他具有较近位置的狄拉克点的材料，例如在单十一含量下的dirace pointer，在黑色的phosphorus，twisted bighosphorus，twisted bighosped begraphene inthemendemendemens中。
We theoretically study the de Haas-van Alphen (dHvA) oscillations in the system with changing the topology of the Fermi surface (the Lifshitz transition) by electron dopings. We employ the two-dimensional tight binding model for $α$-(BEDT-TTF)$_2$I$_3$ under pressure which has two Dirac points in the first Brillouin zone. When this system is slightly doped, there exists two closed Fermi surfaces with the same area and the dHvA oscillations become saw-tooth pattern or inversed saw-tooth pattern for both cases of fixed electron filling ($ν$) or fixed chemical potential ($μ$) with respect to the magnetic field, respectively. By increasing dopings, the system approaches the Lifshitz transition, where two closed Fermi surfaces are close each other. Then, we find that the pattern of the dHvA oscillations changes. A jump of the magnetization appears at the center of the fundamental period and its magnitude increases in the case of the fixed electron filling, while a jump is separated into a pair of jumps and its separation becomes large in the case of the fixed chemical potential. This is due to the lifting of double degeneracy in the Landau levels. Since this lifting is seen in the two-dimensional Dirac fermion system with two Dirac points, the obtained results in this study can be applied to not only $α$-(BEDT-TTF)$_2$I$_3$ but also other materials with closely located Dirac points such as graphene under the uniaxial strain, in black phosphorus, twisted bilayer graphene, and so on.
