{"title":"Floquet-engineered valley topotronics in Kekulé-Y bond textured graphene superlattice","authors":"Sushmita Saha, Alestin Mawrie","doi":"10.1088/1361-6463/ad5e90","DOIUrl":null,"url":null,"abstract":"The exquisite distortion in a Kekulé -Y (Kek-Y) superlattice merges the two inequivalent Dirac cones (from the <italic toggle=\"yes\">K</italic>- and the <italic toggle=\"yes\">K</italic>′- points) into the highest symmetric Γ-point in the hexagonal Brillouin zone. Here, we report that UV circularly polarized light not only opens up a topological gap at the Γ-point, but also lifts the valley degeneracy at that point. Endowed with Floquet dynamics and by devising a scheme of high-frequency approximation, we propose that the left/right-handedness in polarized light offers the possibility to realize valley-selective circular dichroism in a Kek-Y-shaped graphene superlattice. In addition, the non-vanishing Berry curvature and enumeration of the valley-resolved Chern number <inline-formula>\n<tex-math><?CDATA $\\mathcal{C}_{K}/\\mathcal{C}_{K^{\\prime}} = +1/-1$?></tex-math>\n<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mi>K</mml:mi></mml:mrow></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mi>′</mml:mi></mml:msup></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>\n<inline-graphic xlink:href=\"dad5e90ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\n</inline-formula> enable us to assign two pseudospin flavors (up/down) with the two valleys. Thereby, the above observations confirm the topological transition, suggesting the ease of realizing the valley quantum anomalous Hall state within the photon-dressed Kek-Y. These findings further manifest a non-zero optical valley polarization that is maximal at the Γ-point. Our paper thus proposes an optically switchable topological valley filter, which is desired in the evolving landscape of valleytronics.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"26 1","pages":""},"PeriodicalIF":3.1000,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Physics D: Applied Physics","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1088/1361-6463/ad5e90","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, APPLIED","Score":null,"Total":0}
引用次数: 0
Abstract
The exquisite distortion in a Kekulé -Y (Kek-Y) superlattice merges the two inequivalent Dirac cones (from the K- and the K′- points) into the highest symmetric Γ-point in the hexagonal Brillouin zone. Here, we report that UV circularly polarized light not only opens up a topological gap at the Γ-point, but also lifts the valley degeneracy at that point. Endowed with Floquet dynamics and by devising a scheme of high-frequency approximation, we propose that the left/right-handedness in polarized light offers the possibility to realize valley-selective circular dichroism in a Kek-Y-shaped graphene superlattice. In addition, the non-vanishing Berry curvature and enumeration of the valley-resolved Chern number CK/CK′=+1/−1 enable us to assign two pseudospin flavors (up/down) with the two valleys. Thereby, the above observations confirm the topological transition, suggesting the ease of realizing the valley quantum anomalous Hall state within the photon-dressed Kek-Y. These findings further manifest a non-zero optical valley polarization that is maximal at the Γ-point. Our paper thus proposes an optically switchable topological valley filter, which is desired in the evolving landscape of valleytronics.
期刊介绍:
This journal is concerned with all aspects of applied physics research, from biophysics, magnetism, plasmas and semiconductors to the structure and properties of matter.