Fragile topology (FT) opens a new direction in topological photonics, but a new type of photonic crystal (PC) with FT remains to be proposed. In this Letter, the double-site honeycomb lattice (DSHL) PC is proposed by rotating the double dielectric rods (DDR) six times, forming unit cell, and then arraying the unit cells in a triangular lattice. Quantum spin Hall effect occurs by manipulating the DDR in the tangential and radial directions of the unit cell. First, the band structures of DSHL PCs with different structural parameters are calculated, and the laws of topological phase transition are analyzed statistically. Then, to prove the FT properties of two groups of topological nontrivial DSHL PCs, the Wannier-center positions of the bulk bands are calculated by the Wilson-Loop method. Finally, the topological edge states and two groups of topological corner states, which are in the same bulk-state bandgap, are realized successfully. The DSHL PC provides good platforms for both the research of topological photonics and the device design and application, which has a broad prospect.
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http://dx.doi.org/10.1364/OL.434502 | DOI Listing |
ACS Omega
November 2024
Aviation and Automobile School, Chongqing Youth Vocational & Technical College, Chongqing 400044, China.
As a fragile topological state lacking spin-orbit coupling (SOC) and possessing space-time inversion () symmetry, the Stiefel-Whitney (SW) insulator has received much attention. Up until now, the identification of SW insulators has been extensively suggested for 2D phononic systems but has been rarely considered for 3D phononic systems. 3D carbon allotrope 4T57-CA has the capability to achieve nontrivial phononic SW topology, which can be distinguished by a nontrivial second SW number.
View Article and Find Full Text PDFSci Bull (Beijing)
December 2024
School of Physical Science and Technology, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China; Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou 215123, China. Electronic address:
Cells
August 2024
CNRS UMR7284/INSERM U1081, Institute for Research on Cancer and Aging, Nice (IRCAN), Faculty of Medicine, University Côte d'Azur, 06107 Nice, France.
Phys Rev Lett
August 2024
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett
July 2024
Department of Physics, University of California, Berkeley, California 94720, USA.
Van der Waals heterostructures have recently emerged as an exciting platform for investigating the effects of strong electronic correlations, including various forms of magnetic or electrical orders. Here, we perform an unbiased exact diagonalization study of the effects of interactions on topological flat bands of twisted transition metal dichalcogenides (TMDs) at odd integer fillings. For hole-filling ν_{h}=1, we find that the Chern insulator phase, expected from interaction-induced spin-valley polarization of the bare bands, is quite fragile, and gives way to spontaneous multiferroic order-coexisting ferroelectricity and ferromagnetism, in the presence of long-range Coulomb repulsion.
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