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Wang N, Feng F, Wang GP. Nonlocal effective medium theory for phononic temporal metamaterials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 36:105701. [PMID: 37976544 DOI: 10.1088/1361-648x/ad0dcc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/17/2023] [Indexed: 11/19/2023]
Abstract
We have developed a nonlocal effective medium theory (EMT) for phononic temporal metamaterials using the multiscale technique. Our EMT yields closed-form expressions for effective constitutive parameters and reveals these materials as reciprocal media with symmetric band dispersion. Even without spatial symmetry breaking, nonzero Willis coupling coefficients emerge with time modulation and broken time-reversal symmetry, when the nonlocal effect is taken into account. Compared to the local EMT, our nonlocal version is more accurate for calculating the bulk band at high wavenumbers and essential for understanding nonlocal effects at temporal boundaries. This nonlocal EMT can be a valuable tool for studying and designing phononic temporal metamaterials beyond the long-wavelength limit.
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Affiliation(s)
- Neng Wang
- China State Key Laboratory of Radio Frequency Heterogeneous Integration, College of Electronics and Information Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Fanghu Feng
- China State Key Laboratory of Radio Frequency Heterogeneous Integration, College of Electronics and Information Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Guo Ping Wang
- China State Key Laboratory of Radio Frequency Heterogeneous Integration, College of Electronics and Information Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China
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Lin SQ, Tan H, Fu PH, Liu JF. Interaction-driven Chern insulating phases in the α-T3 lattice with Rashba spin-orbit coupling. iScience 2023; 26:107546. [PMID: 37649697 PMCID: PMC10462860 DOI: 10.1016/j.isci.2023.107546] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 07/06/2023] [Accepted: 07/31/2023] [Indexed: 09/01/2023] Open
Abstract
The magnetic interaction is a necessary ingredient to break the time-reversal symmetry in realizing quantum anomalous Hall, or Chern insulating phases. Here, we study topological phases in the α - T 3 model, a minimal theoretical model supporting the flat band, taking account of Rashba spin-orbit coupling and flat-band-induced spontaneous ferromagnetism. By analyzing the interaction-driven phase diagrams, band structures, topological edge states, and topological invariants, we demonstrate that this system offers a platform for realizing a wide range of phases, including normal insulators, semimetals, and Chern insulators. Uniquely, there exist both high-Chern-number insulators and valley-polarized Chern insulators. In the latter phase, edge channels exist in the single valley, leading to nearly 100 % valley polarization. These findings demonstrate the potential of interaction-driven systems in realizing exotic phases and their promising role in future applications in topology electronics and valleytronics.
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Affiliation(s)
- Shi-Qing Lin
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Hui Tan
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Pei-Hao Fu
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
- Science, Mathematics and Technology, Singapore University of Technology and Design, 8 Somapah Road, Singapore City 487372, Singapore
| | - Jun-Feng Liu
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
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Ilan Y. Overcoming randomness does not rule out the importance of inherent randomness for functionality. J Biosci 2019; 44:132. [PMID: 31894113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Randomness is intrinsic to many natural processes. It is also clear that, under certain conditions, disorders are not associated with functionality. Several examples in which overcoming, suppressing, or combining both randomness and non-randomness is required are drawn from various fields. However, the need to suppress or overcome randomness does not negate its importance under certain conditions and its significance in valid processes and organ functions. Randomness should be acknowledged rather than ignored or suppressed; it can be viewed, at worst, as a disturbing disorder that may be treated to produce order, or, at best, as a 'beneficial disorder' that can be considered as a higher level of functionality.
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Affiliation(s)
- Yaron Ilan
- Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel,
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Abstract
We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals (PCs). We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at the Γ point, such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point. The photonic states of such PCs near the Dirac-like point can be described by an effective spin-orbit Hamiltonian of pseudospin-1. The wave propagation in the positive, negative, and zero index media can be unified within a framework of pseudospin-1 description. A scale change in PCs results in a rigid band shift of the Dirac-like cone, allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene. The transport of waves in pseudospin-1 systems exhibits many interesting phenomena, including super Klein tunneling, robust supercollimation, and unconventional Anderson localization. The transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems, which will also be presented for comparison.
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Fang A, Zhang ZQ, Louie SG, Chan CT. Pseudospin-1 Physics of Photonic Crystals. RESEARCH (WASHINGTON, D.C.) 2019; 2019:3054062. [PMID: 31549055 PMCID: PMC6750083 DOI: 10.34133/2019/3054062] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 03/06/2019] [Indexed: 11/06/2022]
Abstract
We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals (PCs). We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at the Γ point, such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point. The photonic states of such PCs near the Dirac-like point can be described by an effective spin-orbit Hamiltonian of pseudospin-1. The wave propagation in the positive, negative, and zero index media can be unified within a framework of pseudospin-1 description. A scale change in PCs results in a rigid band shift of the Dirac-like cone, allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene. The transport of waves in pseudospin-1 systems exhibits many interesting phenomena, including super Klein tunneling, robust supercollimation, and unconventional Anderson localization. The transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems, which will also be presented for comparison.
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Affiliation(s)
- A. Fang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Z. Q. Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Steven G. Louie
- Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
- Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - C. T. Chan
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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Ni X, Purtseladze D, Smirnova DA, Slobozhanyuk A, Alù A, Khanikaev AB. Spin- and valley-polarized one-way Klein tunneling in photonic topological insulators. SCIENCE ADVANCES 2018; 4:eaap8802. [PMID: 29756032 PMCID: PMC5947977 DOI: 10.1126/sciadv.aap8802] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 03/21/2018] [Indexed: 05/12/2023]
Abstract
Recent advances in condensed matter physics have shown that the spin degree of freedom of electrons can be efficiently exploited in the emergent field of spintronics, offering unique opportunities for efficient data transfer, computing, and storage (1-3). These concepts have been inspiring analogous approaches in photonics, where the manipulation of an artificially engineered pseudospin degree of freedom can be enabled by synthetic gauge fields acting on light (4-6). The ability to control these degrees of freedom significantly expands the landscape of available optical responses, which may revolutionize optical computing and the basic means of controlling light in photonic devices across the entire electromagnetic spectrum. We demonstrate a new class of photonic systems, described by effective Hamiltonians in which competing synthetic gauge fields, engineered in pseudospin, chirality/sublattice, and valley subspaces, result in bandgap opening at one of the valleys, whereas the other valley exhibits Dirac-like conical dispersion. We show that this effective response has marked implications on photon transport, among which are as follows: (i) a robust pseudospin- and valley-polarized one-way Klein tunneling and (ii) topological edge states that coexist within the Dirac continuum for opposite valley and pseudospin polarizations. These phenomena offer new ways to control light in photonics, in particular, for on-chip optical isolation, filtering, and wave-division multiplexing by selective action on their pseudospin and valley degrees of freedom.
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Affiliation(s)
- Xiang Ni
- Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA
- Physics Program, Graduate Center of the City University of New York, New York, NY 10016, USA
| | - David Purtseladze
- Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX 78701, USA
| | - Daria A. Smirnova
- Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA
| | - Alexey Slobozhanyuk
- Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA
- Department of Nanophotonics and Metamaterials, ITMO University, St. Petersburg 197101, Russia
| | - Andrea Alù
- Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA
- Physics Program, Graduate Center of the City University of New York, New York, NY 10016, USA
- Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX 78701, USA
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY 10031, USA
| | - Alexander B. Khanikaev
- Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, 140th Street and Convent Avenue, New York, NY 10031, USA
- Physics Program, Graduate Center of the City University of New York, New York, NY 10016, USA
- Corresponding author.
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