论文标题
压力和反转对称性断裂场驱动的一级相变和谷物中狄拉克圆的形成
Pressure and Inversion Symmetry Breaking Field Driven First Order Phase Transition and Formation of Dirac Circle in Perovskites
论文作者
论文摘要
通过模型哈密顿研究和第一原则电子结构计算，我们通过将mapbi $ _3 $作为原型来研究反转对称破坏（ISB）场和静水压力对卤化物钙钛矿的带拓扑的影响。我们的研究表明，尽管静水压力诱导拓扑绝缘子连续过渡，但ISB场使其成为一阶。压力平滑地减少了正常的带隙，并且没有ISB，该系统在其产生具有倒置字符的非平凡带gap之前就达到了无间隙状态。 ISB场不会稳定无间隙状态，因此，带压力的带隙中的不连续性会导致一阶跃迁。此外，在非平凡阶段，ISB场在Trim附近形成一个不变的表面狄拉克圆圈，这是第一个此类圆圈。该圆由类似于AA堆叠双层石墨烯的带拓扑的狄拉克锥的互穿而形成。
Through model Hamiltonian studies and first-principle electronic structure calculations, we have examined the effect of inversion symmetry breaking (ISB) field and hydrostatic pressure on the band topology of halide perovskites by taking MAPbI$_3$ as a prototype. Our study shows that while hydrostatic pressure induces normal to topological insulator continuous phase transition, the ISB field makes it first order. The pressure smoothly reduces the normal bandgap, and without ISB, the system achieves a gapless state before it produces a non-trivial bandgap with inverted characters. The ISB field does not stabilize the gapless state, and therefore, the discontinuity in the bandgap with pressure gives rise to the first-order transition. Furthermore, in the non-trivial phase, the ISB field forms an invariant surface Dirac circle in the neighbourhood of TRIM, which is first of its kind. The circle is formed due to interpenetration of Dirac cones resembling the band topology of AA-stacked bilayer graphene.
