摩尔过渡金属二硫族化物异双层中的弛豫驱动平带与拓扑
Relaxation-driven flat bands and topology in moiré transition metal dichalcogenide heterobilayers
浏览论文内容
中文总结 AI 辅助
该研究针对摩尔TMD异双层，开发了分解晶格弛豫的连续介质模型，揭示其拓扑由本征弛豫驱动，发现赝磁场可产生陈数±1的能隙，为拓扑材料及相关量子态研究提供新框架。
中文摘要 AI 辅助
摩尔过渡金属二硫族化物（TMD）异双层通常用连续介质理论建模，该理论会产生拓扑平庸的能带，这与其同双层形成鲜明对比——同双层具有拓扑能带和分数量子霍尔绝缘体（FCI）。我们表明，这一结论是忽略了晶格弛豫产生的赝磁场所导致的人为结果，而晶格弛豫是所有摩尔材料固有的效应。我们开发了一种连续介质模型，将弛豫分解为三个通道：具有更高傅里叶谐波的修正摩尔势、赝电（标量形变）势和赝磁（矢量）势。以WSe₂/WS₂为原型，我们发现仅赝磁场就能在宽范围的扭转角和晶格失配下使具有±1陈数的第三和第四价带打开能隙，而摩尔势修正和赝电势会缩窄带宽并增大能隙，且通过神经网络变分蒙特卡洛计算证实这些能隙在多体相互作用下依然存在。与刚性模型相比，弛豫还会平滑贝里曲率和量子度量，使能带更接近理想陈极限，这有利于量子反常霍尔效应、FCI态以及更高能带填充时的平带超导电性。我们的工作建立了一个将第一性原理计算通过连续介质模型连接到多体可观测量的新框架，利用该框架证明摩尔异双层是一类全新的拓扑材料，其拓扑完全由本征晶格弛豫驱动。
英文摘要
Moiré transition metal dichalcogenide (TMD) heterobilayers are commonly modeled by a continuum theory that yields topologically trivial bands, in contrast to their homobilayer counterparts which host topological bands and fractional Chern insulators (FCI). We show this conclusion is an artifact of neglecting the pseudomagnetic field generated by lattice relaxation, an effect intrinsic to every moiré material. We develop a continuum model that resolves relaxation into three channels: a modified moiré potential with higher Fourier harmonics, a pseudoelectric (scalar deformation) potential, and a pseudomagnetic (vector) potential. Using WSe$_2$/WS$_2$ as a prototype, we find that the pseudomagnetic field alone gaps the third and fourth valence bands with Chern numbers $\pm 1$ over a broad range of twist angle and lattice mismatch, while the moiré potential correction and pseudoelectric potential narrow the bandwidth and enhance the bandgaps, which survive many-body interactions using neural-network variational Monte Carlo calculations. Relaxation also smoothens the Berry curvature and quantum metric relative to the rigid model, moving the band closer to the ideal Chern limit, beneficial for the quantum anomalous Hall effect, FCI states, and flat-band superconductivity when filled to higher bands. Our work establishes a new framework that connects first-principles calculations, through the continuum model, to many-body observables. Using this framework, we show moiré heterobilayers as a new class of topological materials whose topology is driven entirely by intrinsic lattice relaxation.
发表机构
- University of Minnesota（明尼苏达大学）
- Massachusetts Institute of Technology（麻省理工学院）
- Boston College（波士顿学院）
机构由 AI 辅助整理，请以论文原文为准。
