English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Integer quantum Hall (IQH) states and quantum anomalous Hall (QAH) statesshow the same static (dc) response but distinct dynamical (ac) response. Inparticular, the ac anomalous Hall conductivity profile $\sigma_{yx}(\omega)$ issensitive to the band shape of QAH states. For example, dispersive QAH bandsshows resonance profile without a sign change at the band gap while the IQHstates shows the sign change resonance at the cyclotron energy. We argue byflattening the dispersive QAH bands, $\sigma_{yx}(\omega)$ should recover tothat of flat Landau bands in IQH, thus it is necessary to know the origin ofthe sign change. Taking a topological lattice model with tunable bandwidth, wefound that the origin of the sign change is not the band gap but the Van Hovesingularity energy of the QAH bands. In the limit of small bandwidth, the flatQAH bands recovers $\sigma_{yx}(\omega)$ of the IQH Landau bands. Because ofthe Hall response, these topological bands exhibit giant polarization rotationand ellipticity in the reflected waves (Kerr effect) and rotation in the orderof fine structure constant in the transmitted waves (Faraday effect) withprofile resembles $\sigma_{yx}(\omega)$. Our results serve as a simple guide tooptical characterization for topological flat bands.

Kerr and Faraday rotations in topological flat and dispersive band structures