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Localized heat diffusion in topological thermal materials

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arXiv 2021年

作者： Qi, Minghong Wang, Dong Cao, Pei-Chao Zhu, Xue-Feng Qiu, Cheng-Wei Chen, Hongsheng Li, Ying Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China School of Physics Innovation Institute Huazhong University of Science and Technology Wuhan430074 China Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

Various unusual behaviors of artificial materials are governed by their topological properties, among which the edge state at the boundary of a photonic or phononic lattice has been captivated as a popular notion. However, this remarkable bulk-boundary correspondence and the related phenomena are missing in thermal materials. One reason is that heat diffusion is described in a non-Hermitian framework because of its dissipative nature. The other is that the relevant temperature field is mostly composed of modes that extend over wide ranges, making it difficult to be rendered within the tight-binding theory as commonly employed in wave physics. Here, we overcome the above challenges and perform systematic studies on heat diffusion in thermal lattices. Based on a continuum model, we introduce a state vector to link the Zak phase with the existence of the edge state, and thereby analytically prove the thermal bulk-boundary correspondence. We experimentally demonstrate the predicted edge states with a topologically protected and localized heat dissipation capacity. Our finding sets up a solid foundation to explore the topology in novel heat transfer manipulations. © 2021, CC BY.

关键词： Topology

Second-harmonic generation of structured light by transition-metal dichalcogenide metasurfaces

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Physical Review A 2020年第4期102卷 043508-043508页

作者： Ling Ling Meng Xiaoyan Y. Z. Xiong Tian Xia Qin S. Liu Li Jun Jiang Wei E. I. Sha Weng Cho Chew Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign Illinois 61820 USA Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong China Key Laboratory of Micro-Nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China School of Electrical and Computer Engineering Purdue University Indiana 47907 USA

Structured light characterized by spatially inhomogeneous optical fields found rich applications in optical communication, sensing, microscopy, manipulation, and quantum information. While generation of structured light has been extensively studied in linear optics, the nonlinear optical process, particularly in two-dimensional (2D) materials, is an emerging alternative for generating structured light at shorter wavelengths. In this work, we theoretically demonstrate that radially and azimuthally polarized beams and vortex beams carrying orbital angular momentum could be generated at second-harmonic frequencies by using 2D material-based metasurfaces comprising the same transition-metal dichalcogenide meta-atoms. Manipulation of translations and orientations of anisotropically nonlinear meta-atoms exhibiting a threefold rotation-symmetrical crystalline structure induces strong nonlinear spin-orbital coupling, which enables simultaneous control of spatial phase and polarization in second-harmonic generation. The nonlinear transition-metal dichalcogenide metasurface proposed is promising for on-chip integration of nonlinear generation of structured light.

关键词： Angular momentum of light Metamaterials Nonlinear optics

Graphene based functional devices: A short review

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Frontiers of physics 2019年第1期14卷 23-42页

作者： Rong Wang Xin-Gang Ren Ze Yan Li-Jun Jiang Wei E. I. Sha Guang-Cun Shan Department of Electrical and Electronic Engineering The University of Hong Kong Pokfulam Road Hong Kong China Key Laboratory of Intelligent Computing & Signal Processing Ministry of Education Anhui University Hefei 230039 China School of Instrumentation Science & Opto-electronics Engineering Beihang University Beijing 100191 China Key Laboratory of Micro-nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science & Electronic Engineering Zhejiang University Hangzhou 310027 China California NanoSystem Institute and Department of Chemistry & Biochemistry University of California Los Angeles CA 90095 USA

Graphene is an ideal 2D material system bridging electronic and photonic devices. It also breaks the fundamental speed and size limits by electronics and photonics, respectively. Graphene offers multiple functions of signal transmission, emission, modulation, and detection in a broad band, high speed, compact size, and low loss. Here, we have a brief view of graphene based functional devices at microwave, terahertz, and optical frequencies. Their fundamental physics and computational models were discussed as well.

关键词： graphene terahertz antenna microwave

Coexistence of pseudospin- and valley-Hall-like edge states in a photonic crystal with C3v symmetry

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Physical Review Research 2020年第4期2卷 043148-043148页

作者： Menglin L. N. Chen Li Jun Jiang Zhihao Lan Wei E. I. Sha Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong Department of Electronic and Electrical Engineering University College London London WC1E 7JE United Kingdom Key Laboratory of Micro-nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

We demonstrate the coexistence of pseudospin- and valley-Hall-like edge states in a photonic crystal with C3v symmetry, which is composed of three interlacing triangular sublattices with the same lattice constants. By tuning the geometry of the sublattices, three complete photonic band gaps with nontrivial topology can be created, one of which is due to the band inversion associated with the pseudospin degree of freedom at the Γ point and the other two due to the gapping out of Dirac cones associated with the valley degree of freedom at the K,K′ points. The system can support triband pseudospin- and valley-momentum locking edge states at properly designed domain-wall interfaces. Furthermore, to demonstrate the novel interplay of the two kinds of edge states in a single configuration, we design a four-channel system, where the unidirectional routing of electromagnetic waves against sharp bends between two routes can be selectively controlled by the pseudospin and valley degrees of freedom. Our work combines the pseudospin and valley degrees of freedom in a single configuration and may provide more flexibility in manipulating electromagnetic waves with promising potential for multiband and multifunctional applications.

关键词： Optical & microwave phenomena Photonic crystals Topological effects in photonic systems

Discovery of a maximally charged Weyl point

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arXiv 2022年

作者： Chen, Qiaolu Chen, Fujia Yan, Qinghui Zhang, Li Gao, Zhen Yang, Shengyuan A. Yu, Zhi-Ming Chen, Hongsheng Zhang, Baile Yang, Yihao Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Lab. of Advanced Micro Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen518055 China Research Laboratory for Quantum Materials Singapore University of Technology and Design 487372 Singapore School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore Centre for Disruptive Photonic Technologies The Photonics Institute Nanyang Technological University 50 Nanyang Avenue 639798 Singapore

The hypothetical Weyl particles in high-energy physics have been discovered in three-dimensional crystals as collective quasiparticle excitations near two-fold degenerate Weyl points1-5. Such momentum-space Weyl particles carry quantized chiral charges, which can be measured by counting the number of Fermi arcs emanating from the corresponding Weyl points. It is known that merging unit-charged Weyl particles can create new ones with more charges6. However, only very recently has it been realised that there is an upper limit - the maximal charge number that a two-fold Weyl point can host is four - achievable only in crystals without spin-orbit coupling7-9. Here, we report the experimental realisation of such a maximally charged Weyl point in a three-dimensional photonic crystal. The four charges support quadruple-helicoid Fermi arcs, forming an unprecedented topology of two non-contractible loops in the surface Brillouin zone. The helicoid Fermi arcs also exhibit the long-pursued type-II van Hove singularities that can reside at arbitrary momenta. This discovery reveals a type of maximally charged Weyl particles beyond conventional topological particles in crystals. Copyright © 2022, The Authors. All rights reserved.

关键词： Topology

Dipole-matter interactions governed by the asymmetry of Maxwell equations

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arXiv 2023年

作者： Zhong, Yuhan Wang, Chan Bian, Chenxu Chen, Xuhuinan Chen, Jialin Zhu, Xingjian Hu, Hao Low, Tony Chen, Hongsheng Zhang, Baile Lin, Xiao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy at Zhejiang University Zhejiang University Haining314400 China Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Department of Electrical and Computer Engineering Technion-Israel Institute of Technology Haifa32000 Israel School of Physics Zhejiang University Hangzhou310027 China School of Electrical and Electronic Engineering Nanyang Technological University Singapore639798 Singapore Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Department of Physics University of Minnesota MinneapolisMN55455 United States Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Centre for Disruptive Photonic Technologies Nanyang Technological University Singapore637371 Singapore

Directionally molding the near-field and far-field radiation lies at the heart of nanophotonics and is crucial for applications such as on-chip information processing and chiral quantum networks. The most fundamental model for radiating structures is a dipolar source located inside a homogeneous matter. However, the influence of matter on the directionality of dipolar radiation is oftentimes overlooked, especially for the near-field radiation. We show that the dipole-matter interaction is intrinsically asymmetric and does not fulfill the duality principle, originating from the inherent asymmetry of Maxwell’s equations, i.e., electric charge and current are ubiquitous but their magnetic counterparts are non-existent to elusive. Moreover, we find that the asymmetric dipole-matter interaction could offer an enticing route to reshape the directionality of not only the near-field radiation but also the far-field radiation. As an example, both the near-field and far-field radiation directionality of Huygens dipole (located close to a dielectric-metal interface) would be reversed, if the dipolar position is changed from the dielectric region to the metal region. © 2023, CC BY.

关键词： Maxwell equations

A perspective of twisted photonic structures

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arXiv 2021年

作者： Chen, Jialin Lin, Xiao Chen, Mingyuan Low, Tony Chen, Hongsheng Dai, Siyuan Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy at Zhejiang University Zhejiang University Haining314400 China Materials Research and Education Center Department of Mechanical Engineering Auburn University AuburnAL36849 United States Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States

Moiré superlattices-twisted van der Waals (vdW) structures with small angles-are attracting increasing attention in condensed matter physics, due to important phenomena revealed therein, including unconventional superconductivity, correlated insulating states, and ferromagnetism. Moiré superlattices are typically comprised of atomic layers of vdW materials where the exotic physics arises from the quantum electronic coupling between adjacent atomic layers. Recently, moiré electronics has motivated their photonic counterparts. In addition to vdW materials, twisted photonic systems can also be comprised of metamaterials, metasurfaces, and photonic crystals, mediated by interlayer electromagnetic coupling instead. The interplay between short-ranged interlayer quantum and long-ranged electromagnetic coupling in twisted structures are expected to yield rich phenomena in nano-optics. This perspective reviews recent progress in twisted structures for nanophotonics and outlooks emerging topics, opportunities, fundamental challenges, and potential applications. © 2021, CC BY.

关键词： Van der Waals forces

Erasable superconductivity in topological insulator Bi2Se3 induced by voltage pulse

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Research Square

Research Square 2020年

作者： Le, Tian Ye, Qikai Chen, Chufan Yin, Lichang Zhang, Dongting Wang, Xiaozhi Lu, Xin Center for Correlated Matter and Department of Physics Zhejiang University Hangzhou310058 China Key Labaratory of Advanced Micro/Nano Electronic Devices and Smart Systems of Zhejiang College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Zhejiang Province Key Laboratory of Quantum Technology and Device Zhejiang University Hangzhou310027 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China

Three-dimensional topological insulators (TIs) attract much attention due to its topologically protected Dirac surface states [1, 2, 3, 4]. Doping into TIs or their proximity with normal superconductors can promote the realization of topological superconductivity (SC) and Majorana fermions with potential applications in quantum computations [5, 6, 7, 8, 9, 10, 11]. Here, we observed an emergent superconductivity in local mesoscopic point-contacts on the topological insulator Bi2Se3 by applying a voltage pulse through the contacts, evidenced by the Andreev reflection peak in the point-contact spectra and a visible resistance drop in the four-probe electrical resistance measurements. More intriguingly, the superconductivity can be erased with thermal cycles by warming up to high temperatures (300 K) and induced again by the voltage pulse at the base temperature (1.9 K), suggesting a significance for designing new types of quantum devices. Nematic behaviour is also observed in the superconducting state, similar to the case of CuxBi2Se3 as topological superconductor candidates [12, 13, 14, 15, 16, 11, 17, 18]. © 2020, CC BY.

关键词： Bismuth compounds

Photonic antiferromagnetic topological insulator with a single surface Dirac cone

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Science advances 2025年第22期11卷 eadu6230页

作者： Fujia Chen Ning Han Songyang Pu Rui Zhao Li Zhang Qiaolu Chen Yuze Hu Mingyu Tong Wenhao Li Junyao Wu Yudong Ren Xinrui Li Wenyan Yin Hongsheng Chen Rui-Xing Zhang Yihao Yang State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou 310027 China. International Joint Innovation Center The Electromagnetics Academy at Zhejiang University Zhejiang University Haining 314400 China. Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua 321099 China. College of Optical and Electronic Technology China Jiliang University Hangzhou 310018 China. Department of Physics and Astronomy The University of Tennessee Knoxville TN 37996 USA. Department of Materials Science and Engineering The University of Tennessee Knoxville TN 37996 USA.

Antiferromagnetism, characterized by alternating magnetic moments, has garnered renewed interest for its potential applications in spintronics and axion electrodynamics. Its synergy with topology may yield an exotic topological phase unique to a certain magnetic order, termed antiferromagnetic topological insulators (AF TIs). A hallmark signature of AF TIs is the presence of a single surface Dirac cone-a feature typically associated with strong three-dimensional (3D) topological insulators but lacking direct observation. Here, we theoretically and experimentally discover a 3D photonic AF TI protected by the combined symmetry of time reversal and half-lattice translation. By measuring both bulk and surface states, we directly observe the symmetry-protected single-Dirac-cone surface states and their remarkable robustness against random magnetic disorders. To our knowledge, our work constitutes the first realization of photonic AF TIs and photonic analogs of strong 3D topological insulators, opening a chapter for exploring topological photonic devices and phenomena incorporating additional magnetic degrees of freedom.

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