α - T₃晶格中交错势和椭圆光驱动的拓扑相变
Staggered Potential and Elliptical Light Driven Topological Phase Transitions in $α$-$\mathcal{T}_{3}$ Lattice
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中文总结 AI 辅助
研究六方氮化硼对α - T₃晶格电子性质影响，通过交错势和椭圆光驱动实现拓扑相变，确定几何奇点及不同陈数拓扑相转变条件，还指出拓扑相特征及热电塞贝克响应可作为实验指纹，为实现高陈数相提供框架。
中文摘要 AI 辅助
我们从理论上研究了六方氮化硼（h - BN）对由非共振椭圆偏振光场驱动的α - T₃晶格电子性质的影响。交错势M打破了子晶格反演对称性，将初始半金属转变为陈数C = 0的平凡绝缘体。我们确定了α = 1/√2处的一个基本几何奇点，与M无关，在此之下没有有限驱动能关闭下带隙，形成一个稳定的拓扑窗口，传导 - 平带反转产生陈数C = 1的陈绝缘体。高于此临界值，下带隙在有限强度下关闭，随着接近骰子极限（α = 1），允许从C = 1转变为C = 2。拓扑相的特征是在σxy = e²/h（C = 1）和σxy = 2e²/h（C = 2）处有量子化的反常霍尔平台，每个谷恰好贡献1/2 e²/h。C = 1的平台在从0 K到300 K时保持稳健，而C = 2由于其较窄的带隙需要T < 100 K。高度不对称的热电塞贝克响应进一步作为每个相的实验指纹，为在衬底支撑的α - T₃材料中实现稳定的高陈数相提供了一个现实的框架。
英文摘要
We theoretically investigate the influence of hexagonal boron nitride (h-BN) on the electronic properties of an $α$-$\text{T}_3$ lattice driven by an off-resonant elliptically polarized light field. The staggered potential $M$ breaks the sublattice inversion symmetry, transforming the initial semimetal into a trivial insulator with Chern number $C = 0$. We identify a fundamental geometric singularity at $α= 1/\sqrt{2}$, independent of $M$, where the valley-resolved lower-gap threshold diverges, bounding a finite topological window where conduction--flat band inversion yields a Chern insulator with $C = 1$ carried by the flat band. Increasing the drive further closes the lower gap at the $K'$ valley, transferring the index to the valence band so that the flat band becomes trivial while the system remains $C = 1$. For $α> 1/\sqrt{2}$ the lower gap closes at finite intensity, allowing a transition to $C = 2$ as the dice limit ($α= 1$) is approached. The topological phases are characterized by quantized anomalous Hall plateaus at $σ_{xy} = e^2/h$ ($C = 1$) and $σ_{xy} = 2e^2/h$ ($C = 2$). The $C = 1$ plateau sits in a narrow gap and is the most fragile, while the $C = 2$ plateau is protected by a wider gap and remains robust to room temperature. A highly asymmetric thermoelectric Seebeck response further serves as an experimental fingerprint of each phase, providing a realistic framework for realizing stable high-Chern-number phases in substrate-supported $α$-$\text{T}_3$ materials.
