双层Lieb晶格中的层分辨拓扑金属
Layer-Resolved Topological Metals in the Bilayer Lieb Lattice
AI总结：
研究双层Lieb晶格中的拓扑金属相，通过分析有无OAM依赖耦合时的情况，发现其能形成不同状态并展示不对称边界态，为层分辨拓扑无隙相的可控工程提供了途径。
AI中文摘要：
我们在双层Lieb晶格中识别出一个二维时间反演不变拓扑金属相，其特征为层分辨的赝自旋陈数被量子化。在没有轨道角动量依赖（OAM依赖）耦合时，系统产生一个零间接带隙且赝自旋陈数被量子化的时间反演不变拓扑半金属。相反符号的层内OAM依赖耦合会将零间接带隙半金属转变为金属。该模型还展示了不对称边界态。这些结果为合成材料和量子材料中层分辨拓扑无隙相的可控工程开辟了道路。
英文摘要：
We identify a two-dimensional time-reversal-invariant topological metallic phase on a bilayer Lieb lattice, characterized by a quantized layer--resolved pseudo-spin Chern number. Without the orbital-angular-momentum-dependent (OAM-dependent) coupling, the system gives rise to a time-reversal-invariant topological semimetal with a zero indirect gap and quantized pseudo-spin Chern number. Opposite-sign intralayer OAM-dependent coupling immediately converts the zero-indirect-gap semimetal into a metal, in which the global spectrum is metallic while the layer--resolved pseudo-spin Chern number remains well defined as long as the direct gap at each crystal momentum and the pseudo-spin gap remain open. The model also exhibits asymmetric boundary states: in the semimetallic regime, one edge hosts perfectly flat bands, whereas the opposite edge supports gapless counter-propagating modes forming a one-dimensional Dirac cone. An edge-localized interlayer coupling gaps only the counter-propagating edge states, leaving the flat-band edge essentially intact, while intralayer OAM-dependent coupling bends the exact flat band into a dispersive boundary mode without affecting the gapped Dirac edge. These results open a route toward the controlled engineering of layer--resolved topological gapless phases in synthetic and quantum materials.
