Faraday rotations, ellipticity and circular dichroism in the magneto-optical spectrum of moiré superlattices

Flat bands and chiral optical response of moiré insulators

We present a low-energy model describing the reconstruction of the electronic spectrum in twisted bilayers of honeycomb crystals with broken sublattice symmetry. The resulting moiré patterns are classified into two families with different symmetry. In both cases, flat bands appear at relatively large angles, without any magic angle condition. Transitions between them give rise to sharp resonances in the optical absorption spectrum at frequencies well below the gap of the monolayer. Owing to their chiral symmetry, twisted bilayers display circular dichroism, i.e., different absorption of left a…

Faraday Rotation and Circular Dichroism Spectra of Gold and Silver Nanoparticle Aggregates

We study the magneto-optical response of noble metal nanoparticle clusters. We consider the interaction between the light-induced dipoles of particles. In the presence of a magnetic field, the simplest achiral cluster, a dimer, exhibits circular dichroism (CD). The CD of a dimer depends on the directions of the magnetic field and the light wave vector. The CD of a populous cluster weakly depends on the magnetic field. Upon scattering from the cluster, an incident linearly polarized light with polarization azimuth $φ$, becomes elliptically polarized. The polarization azimuth rotation and ellipt…

$p$波磁体中的量子几何与椭圆光学二色性

Quantum geometry and elliptic optical dichroism in $p$-wave magnets

研究$p$波磁体在椭圆偏振光辐照下的光学吸收，推导光学电导率解析公式，发现当Néel矢量沿$y$轴时出现完美椭圆光学二色性，从而可通过测量椭圆度确定Néel矢量。

M谷扭曲过渡金属二硫属化物的莫尔能带理论

Moiré band theory for M-valley twisted transition metal dichalcogenides

本文提出用第IV族/IVB族三角TMDs（Zr、Hf、Sn的硫/硒化物）扭曲双层构建莫尔材料，通过DFT导出莫尔周期哈密顿量，揭示其六味导带态解耦及自发谷极化以输运各向异性为标志。

Light-Induced Ferromagnetism in Moiré Superlattices

Many-body interactions between carriers lie at the heart of correlated physics. The ability to tune such interactions would open the possibility to access and control complex electronic phase diagrams on demand. Recently, moiré superlattices formed by two-dimensional materials have emerged as a promising platform for quantum engineering such phenomena. The power of the moiré system lies in the high tunability of its physical parameters by tweaking layer twist angle, electrical field, moiré carrier filling, and interlayer coupling. Here, we report that optical excitation can drastically tune th…

交变磁体中的自旋选择性椭圆光学二色性和完全自旋极化的三阶非线性光电流

Spin-selective elliptic optical dichroism and perfectly spin-polarized third-order nonlinear photocurrent in altermagnets

基于d波交变磁体的低能理论，发现自旋选择性椭圆二色性，并通过量子度量和贝里曲率公式证明在椭圆偏振光和静电场下产生完全自旋极化的三阶光电流。