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Observation of Multiple Topological Corner States in Thermal Diffusion

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arXiv 2023年

作者： Qi, Minghong Wang, Yanxiang Cao, Pei-Chao Zhu, Xue-Feng Gao, Fei Chen, Hongsheng Li, Ying Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China School of Physics Innovation Institute Huazhong University of Science and Technology Wuhan430074 China

Higher-dimensional topological meta-materials have more flexible than one-dimensional topological materials, which are more convenient to apply and solve practical problems. However, in diffusion systems, higher-dimensional topological states have not been well studied. In this work, we experimentally realized the 2D topological structure based on a kagome lattice of thermal metamaterial. Due to the anti-Hermitian properties of the diffusion Hamiltonian, it has purely imaginary eigenvalues corresponding to the decay rate. By theoretical analysis and directly observing the decay rate of temperature through experiments, we present the various corner states in 2D topological diffusive system. Our work constitutes the first realization of multiple corner states with high decay rates in a pure diffusion system, which provides a new idea for the design of topological protected thermal metamaterial in the future. © 2023, CC BY.

关键词： Metamaterials

Observing parity-time symmetry in diffusive systems

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arXiv 2023年

作者： Cao, Pei-Chao Ju, Ran Wang, Dong Qi, Minghong Liu, Yun-Kai Peng, Yu-Gui Chen, Hongsheng Zhu, Xue-Feng Li, Ying School of Physics Innovation Institute Huazhong University of Science and Technology Wuhan430074 China Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China

Phase modulation has scarcely been mentioned in diffusive systems since the diffusion process does not carry momentum like waves. Recently, the non-Hermitian physics provides a new perspective for understanding diffusion and shows prospects in the phase regulation of heat flow, for example, the discovery of anti-parity-time (APT) symmetry in diffusive systems. The precise control of thermal phase however remains elusive hitherto and can hardly be realized in APT-symmetric thermal systems due to the existence of phase oscillation. Here we construct the counterpart of APT-symmetric diffusive systems, i.e., PT-symmetric diffusive systems, which can achieve complete suppression of thermal phase oscillation. We find the real coupling of diffusive fields can be readily established through a strong convective background, where the decay-rate detuning is enabled by thermal metamaterial design. Moreover, we observe phase transition of PT symmetry breaking in diffusive systems with the symmetry-determined amplitude distribution and phase regulation of coupled temperature fields. Our work uncovers the existence of PT-symmetry in dissipative energy exchanges and provides a unique approach for harnessing the mass transfer of particles, the wave propagation in strongly scattering systems as well as thermal conduction. © 2023, CC BY.

关键词： Wave propagation

Topologically protected edge states in time photonic crystals with chiral symmetry

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arXiv 2025年

作者： Yang, Yukun Hu, Hao Liu, Liangliang Yang, Yihao Yu, Youxiu Long, Yang Zheng, Xuezhi Luo, Yu Li, Zhuo Garcia-Vidal, Francisco J. National Key Laboratory of Microwave Photonics College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics Nanjing211106 China State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Department of Electrical Engineering KU Leuven Leuven3001 Belgium Universidad Autónoma de Madrid MadridE-28049 Spain

Time photonic crystals are media in which their electromagnetic parameters are modulated periodically in time, showing promising applications in non-resonant lasers and particle accelerators, among others. Traditionally utilized to study space photonic crystals, topological band theory has also been translated recently to analyze time photonic crystals with time inversion symmetry, enabling the construction of the temporal version of topological edge states. However, temporal disorder can readily break time inversion symmetry in practice, hence likely destroying the edge states associated with this type of time photonic crystals. To overcome this limitation, here we propose a new class of time photonic crystals presenting chiral symmetry instead, whose edge states exhibit superior robustness over the time-reversal-symmetry-protected counterparts. Our time photonic crystal is equivalent to a temporal version of the Su-Schrieffer-Heeger model, and the chiral symmetry of this type of time photonic crystals quantizes the winding number defined in the Bloch frequency band. Remarkably, random temporal disorders do not impact the eigenfrequencies of these chiral-symmetry-protected edge states, while instead enhancing their temporal localizations. Our findings thus provide a promising paradigm to control field amplification with exceptional robustness as well as being a feasible platform to investigate various topological phases in time-varying media. Copyright © 2025, The Authors. All rights reserved.

关键词： Topology

SELF-DRIVING TECH FOR NON-CARS From mall shuttles to monster trucks, Perrone Robotics is ready to debut its self-driving tech

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IEEE SPECTRUM 2019年第3期56卷 9-10页

作者： Ross, Philip E. Key Laboratory of Advanced Micro/Nano Electronic Devices and Smart Systems of Zhejiang College of Information Science and Electronic Engineering Zhejiang University Hangzhou China

Like early mammals scuttering between the legs of tyrannosaurs, a lot of little companies are trying to weave around-and maybe even outlast-the big boys of self-driving technology.

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Boundary-induced topological chiral extended states in Weyl metamaterial waveguides

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arXiv 2024年

作者： Han, Ning Chen, Fujia Li, Mingzhu Zhao, Rui Li, Wenhao Chen, Qiaolu Zhang, Li Pan, Yuang Ma, Jingwen Yu, Zhi-Ming Chen, Hongsheng Yang, Yihao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China School of Information and Electrical Engineering Hangzhou City University Hangzhou310015 China Department of Electronic Engineering The Chinese University of Hong Kong Shatin New Territories Hong Kong 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

In topological physics, it is commonly understood that the existence of the boundary states of a topological system is inherently dictated by its bulk. A classic example is that the surface Fermi-arc states of a Weyl system are determined by the chiral charges of Weyl points within the bulk. Contrasting with this established perspective, here, we theoretically and experimentally discover a family of topological chiral bulk states extending over photonic Weyl metamaterial waveguides, solely induced by the waveguide boundaries, independently of the waveguide width. Notably, these bulk states showcase discrete momenta and function as "wormhole" tunnels that connect Fermi-arc surface states living in different two-dimensional (2D) spaces via a third dimension. Our work offers a magnetic-field-free mechanism for robust chiral bulk transport of waves and highlights the boundaries as a new degree of freedom to regulate bulk Weyl quasiparticles. Copyright © 2024, The Authors. All rights reserved.

关键词： Metamaterials

Asymmetric Heat Transfer with Linear Conductive Metamaterials

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Physical Review Applied 2023年第3期20卷 034013-034013页

作者： Yishu Su Ying Li Minghong Qi Sebastien Guenneau Huagen Li Jian Xiong Center for Composite Materials and Structures Harbin Institute of Technology Harbin 150001 China Interdisciplinary Center for Quantum Information 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 Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy of Zhejiang University Zhejiang University Haining 314400 China UMI 2004 Abraham de Moivre-CNRS Imperial College London London SW7 2AZ United Kingdom Department of Electrical and Computer Engineering National University of Singapore Singapore 117583 Singapore

Asymmetric heat-transfer systems, often referred to as thermal diodes or thermal rectifiers, have garnered increasing interest due to their wide range of application possibilities. Most of those previous macroscopic asymmetric thermal devices either resort to nonlinear thermal conductivities with strong temperature dependence that may be quite limited by or fixed in natural materials or rely on active modulation that necessitates auxiliary energy payloads. Here, we establish a straightforward strategy of passively realizing asymmetric heat transfer with linear conductive materials. The strategy also introduces an interrogative perspective into the previous design of passive asymmetric heat transfer utilizing nonlinear thermal conductivity, correcting the misconception that thermal rectification is impossible with separable nonlinear thermal conductivity. The nonlinear-perturbation mode can be versatilely engineered to produce an effective and wide-ranging perturbation in heat conduction, which imitates and bypasses intrinsic thermal nonlinearity constraints set by naturally occurring counterparts. Independent experimental characterizations of surface thermal radiation and thermal convection verify that heat exchange between a graded linear thermal metamaterial and the ambient surroundings can be tailored to achieve macroscopic asymmetric heat transfer. Our work is envisaged to inspire conceptual models for heat-transfer control, serving as a robust and convenient platform for advanced thermal management and thermal computation.

关键词： Heat radiation Heat transfer Metamaterials Thermal conductivity

Observation of non-Abelian band topology without time-reversal symmetry

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arXiv 2024年

作者： Hu, Yuze Tong, Mingyu Jiang, Tian Jiang, Jian-Hua Chen, Hongsheng Yang, Yihao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China Institute for Quantum Science and Technology College of Science National University of Defense Technology Changsha410073 China Suzhou Institute for Advanced Research University of Science and Technology of China Suzhou215123 China School of Physical Science and Technology Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou215006 China International Joint Innovation Center The Electromagnetics Academy at Zhejiang university Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China

Going beyond the conventional theory, non-Abelian band topology uncovers the global quantum geometry of Bloch bands with multiple gaps and thus unveil a new paradigm for topological physics. However, to date, all non-Abelian topological materials are restricted to systems with time-reversal symmetry (T). Here, starting from a Kagome lattice inspired by Haldane model and designer gyromagnetic photonic crystals (PhCs), we show that T breaking can lead to rich non-Abelian topological physics, particularly the emergence of multigap antichiral edge states. Simply changing the magnetic flux of the Kagome lattice, or in-situ tuning the local magnetic field of the gyromagnetic PhCs, can lead to the unconventional creation, braiding, merging, and splitting of non-Abelian charged band nodes, alongside with the direct manipulation of the multigap antichiral edge states. Particularly, the quadratic point can be split into four Dirac points, a phenomenon unique in T-broken systems. Our theoretical and experimental findings will inspire a new direction in the study of non-Abelian physics in T-broken systems and open an unprecedent pathway for topological manipulation of electromagnetic waves. Copyright © 2024, The Authors. All rights reserved.

关键词： Topology

Observation of Non-Hermitian Skin Effect in Thermal Diffusion

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arXiv 2023年

作者： Liu, Yun-Kai Cao, Pei-Chao Qi, Minghong Huang, Qiang-Kai-Lai Peng, Yu-Gui Li, Ying Zhu, Xue-Feng School of Physics Innovation Institute Huazhong University of Science and Technology Wuhan430074 China Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute Zhejiang University Jinhua321099 China Shaoxing Institute Zhejiang University Shaoxing312000 China

The paradigm shift of the Hermitian systems into the non-Hermitian regime profoundly modifies the inherent topological property, leading to various unprecedented effects such as the non-Hermitian skin effect (NHSE). In the past decade, the NHSE effect has been demonstrated in quantum, optical and acoustic systems. Besides in those non-Hermitian wave systems, the NHSE in diffusive systems has not yet been explicitly demonstrated, despite recent abundant advances in the study of topological thermal diffusion. Here we first design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model which enables the observation of diffusive NHSE. In the proposed model, the periodic heat exchange rate among adjacent unit cells and the asymmetric temperature field coupling inside unit cells can be judiciously realized by appropriate configurations of structural parameters of unit cells. The transient concentration feature of temperature field on the boundary regardless of initial excitation conditions can be clearly observed, indicating the occurrence of transient thermal skin effect. Nonetheless, we experimentally demonstrated the NHSE and verified the remarkable robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others. Copyright © 2023, The Authors. All rights reserved.

关键词： Acoustic fields

Real higher-order Weyl photonic crystal

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arXiv 2023年

作者： Pan, Yuang Cui, Chaoxi Chen, Qiaolu Chen, Fujia Zhang, Li Ren, Yudong Han, Ning Li, Wenhao Li, Xinrui Yu, Zhi-Ming Chen, Hongsheng Yang, Yihao Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou310027 China International Joint Innovation Center The Electromagnetics Academy Zhejiang University Zhejiang University Haining314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing312000 China 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

Higher-order Weyl semimetals are a family of recently predicted topological phases simultaneously showcasing unconventional properties derived from Weyl points, such as chiral anomaly, and multidimensional topological phenomena originating from higher-order topology. The higher-order Weyl semimetal phases, with their higher-order topology arising from quantized dipole or quadrupole bulk polarizations, have been demonstrated in phononics and circuits. Here, we experimentally discover a class of higher-order Weyl semimetal phase in a three-dimensional photonic crystal (PhC), exhibiting the concurrence of the surface and hinge Fermi arcs from the nonzero Chern number and the nontrivial generalized real Chern number, respectively, coined a real higher-order Weyl PhC. Notably, the projected two-dimensional subsystem with kz = 0 is a real Chern insulator, belonging to the Stiefel-Whitney class with real Bloch wavefunctions, which is distinguished fundamentally from the Chern class with complex Bloch wavefunctions. Our work offers an ideal photonic platform for exploring potential applications and material properties associated with the higher-order Weyl points and the Stiefel-Whitney class of topological phases. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology