Quantized electric multipole insulators
TLDR
This work introduces a paradigm in which “nested” Wilson loops give rise to topological invariants that have been overlooked and opens a venue for the expansion of the classification of topological phases of matter.Abstract:
The Berry phase provides a modern formulation of electric polarization in crystals. We extend this concept to higher electric multipole moments and determine the necessary conditions and minimal models for which the quadrupole and octupole moments are topologically quantized electromagnetic observables. Such systems exhibit gapped boundaries that are themselves lower-dimensional topological phases. Furthermore, they host topologically protected corner states carrying fractional charge, exhibiting fractionalization at the boundary of the boundary. To characterize these insulating phases of matter, we introduce a paradigm in which “nested” Wilson loops give rise to topological invariants that have been overlooked. We propose three realistic experimental implementations of this topological behavior that can be immediately tested. Our work opens a venue for the expansion of the classification of topological phases of matter.read more
Citations
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Topological Photonics on a Small Scale
TL;DR: In this article, the physics and realisation of topological photonics on small scales, with the dimensions often smaller or comparable with the wavelength of light, are discussed, and a novel photonic platform employing higher-order topological effects for creating subwavelength highly efficient topologically protected optical cavities.
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Second-Order Topological Photonic Modes in Dipolar Arrays
TL;DR: Higher-order topological insulators (HOTIs) as mentioned in this paper have novel topological boundary states on the hinges and corners, and they generalize them to photonic HOTIs beyond conventional sc...
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Antiferromagnetic second-order topological insulator with fractional mass-kink
TL;DR: In this paper , a fractional mass-kink induced 2D SOTI in monolayer FeSe with canted checkerboard antiferromagnetic (AFM) order by analytic model and first-principles calculations is reported.
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Magnetism-mediated transition between crystalline and higher-order topological phases in NpSb
Ning Mao,Xiangting Hu,H. H. Wang,Ying Dai,Baibiao Huang,Yuriy Mokrousov,Yuriy Mokrousov,Chengwang Niu +7 more
TL;DR: In this paper, the authors identify layered NpSb as a two-dimensional topological crystalline insulator with intrinsic ferromagnetic order with a band gap which is as large as 220 meV.
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Robustness of topological corner modes in photonic crystals
Matthew Proctor,Paloma A. Huidobro,Barry Bradlyn,María Blanco de Paz,Maia G. Vergniory,Maia G. Vergniory,Dario Bercioux,Dario Bercioux,Aitzol García-Etxarri,Aitzol García-Etxarri +9 more
TL;DR: In this paper, the robustness of corner modes in higher-order topological photonic crystals was analyzed and it was shown that these systems are reducible to a chirally symmetric limit.
References
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Maximally localized generalized Wannier functions for composite energy bands
Nicola Marzari,David Vanderbilt +1 more
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Theory of polarization of crystalline solids
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