Article
Acoustics
Yafeng Chen, Jie Zhu, Zhongqing Su
Summary: This study designs four new types of second-order phononic topological insulators (SPTIs) with customized dual-bandgap, allowing for dual-band corner states and potential applications in multiband communications and manipulation of elastic waves with enhanced robustness.
JOURNAL OF SOUND AND VIBRATION
(2023)
Review
Nanoscience & Nanotechnology
Yafeng Chen, Zhihao Lan, Zhongqing Su, Jie Zhu
Summary: This article discusses the recent advances and achievements in the development of photonic and phononic topological insulators using inverse design methodologies. It covers one-dimensional TIs, TIs based on the quantum spin Hall effect and quantum valley Hall effect, as well as high-order TIs in lattices with diverse symmetries. Several inversely designed photonic and phononic TIs with superior performance are showcased, and the future of this emerging research field is also discussed.
Article
Physics, Applied
Jianghua Li, Minquan Kuang, Jingbo Bai, Guangqian Ding, Hongkuan Yuan, Chengwu Xie, Wenhong Wang, Xiaotian Wang
Summary: In this Letter, we propose that the NiZrCl6 monolayer is a 2D ferromagnetic material with rich second-order topological phases (SOTPs). The SOTP nature in the NiZrCl6 monolayer is resistant to the spin-orbit coupling effect. This finding is important for exploring higher-order topological phases in 2D magnetic and phononic systems.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Yuanyuan Shen, Shengguo Guan, Chunyin Qiu
Summary: In this study, the experimental investigation on topological valley transport of spoof surface acoustic waves (SAWs) is reported. The valley pseudospins and valley Hall phase transition are achieved by adjusting the structural size of adjacent grooves. Aside from the direct visualization of the vortex chirality-locked beam splitting for the bulk valley states, valley-projected edge states are also observed in straight and bent interface channels formed by two topologically distinct valley Hall insulating phases. The experimental data are in good agreement with the numerical predictions. The topological transport of spoof SAWs, encoded with valley information, provides more possibilities in designing novel acoustic devices based on valley-contrasting physics.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Zichong Yue, Zhiwang Zhang, Hai-Xiao Wang, Wei Xiong, Ying Cheng, Xiaojun Liu
Summary: Research on the application of higher-order topological insulators in acoustic systems is highly significant. This study proposes a new design scheme for acoustic SOTIs and observes the state switching process experimentally. The results demonstrate the robustness of topological corner states in the presence of defects.
NEW JOURNAL OF PHYSICS
(2022)
Article
Physics, Multidisciplinary
Xiao Li, Shiqiao Wu, Guanqing Zhang, Wanzhu Cai, Jack Ng, Guancong Ma
Summary: Experimental measurements were conducted on coupling effects of topological corner modes (TCMs) in two different types of two-dimensional acoustic HOTIs, revealing differences in their topological invariants and response line shapes. A theoretical link between the topological invariants and the coupled TCMs' response line shape was established and experimentally confirmed, providing a pathway to distinguish HOTIs experimentally.
FRONTIERS IN PHYSICS
(2021)
Article
Engineering, Mechanical
Hongbo Huang, Shaoyong Huo, Jiujiu Chen
Summary: This research introduces a new design of ternary valley-Hall phononic crystals that achieve subwavelength negative refraction and establish defect-immune topological negative refraction. The study also demonstrates mode conversion from longitudinal to transverse waves and designs a topological elastic valley filter using valley-selective excitation.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2021)
Article
Physics, Applied
Xiao-Lei Tang, Tian-Xue Ma, Yue-Sheng Wang
Summary: In this work, the topological rainbow trapping and energy amplification of acoustic waves in a gradient phononic crystal structure is investigated numerically and experimentally. Topological interface states (TISs) are generated along the interface between two phononic crystals with different topological phases due to the acoustic valley Hall effect. Rainbow trapping is achieved by introducing gradient into a 3D-printed phononic crystal structure by varying the geometrical parameter of scatterers along the interface. Incident acoustic waves at different frequencies split, stop, and are significantly amplified at different positions. Importantly, the rainbow trapping of TISs is immune to random structural disorders. The topological rainbow trapping shows promise for the design of broadband energy harvesters with excellent robustness.
APPLIED PHYSICS LETTERS
(2023)
Article
Optics
Shi-lei Shen, Chao Li, Jun-Fang Wu
Summary: This study investigates the influence of BNN interaction on photonic higher-order corner states, finding two kinds of corner states different from traditional zero-energy state, and designing a novel structure to distinguish contributions from NNN hopping and PEC boundaries. The total contribution on corner states when NNN couplings and PEC boundaries coexist is also examined, revealing some interesting features that may expand understanding of high-order corner modes in a more general framework.
Article
Engineering, Mechanical
Seongmin Park, Wonju Jeon
Summary: We propose deep-subwavelength phononic beams that support topological interface states (TISs) at ultra-low frequencies. The beams are designed using unit cells with acoustic black hole (ABH) configurations to obtain the first band gap at low frequencies, where the unit cell size is much smaller than the wavelength of the wave. By modifying the ABH configuration and breaking the inversion symmetry of the unit cell, we control the topological phases of the phononic beams and connect two topologically distinct beams to produce the TIS in their low band gaps.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2023)
Article
Physics, Multidisciplinary
Yating Yang, Jiuyang Lu, Mou Yan, Xueqin Huang, Weiyin Deng, Zhengyou Liu
Summary: The study introduces a new type of topological insulator in a bilayer phononic crystal, which combines first-order and second-order topological features, with one-dimensional edge states and zero-dimensional corner states existing simultaneously in the same system.
PHYSICAL REVIEW LETTERS
(2021)
Article
Energy & Fuels
Binsheng Li, Hui Chen, Baizhan Xia, Lingyun Yao
Summary: Recently, topological phononic crystals have been widely used for designing acoustic energy harvesting devices, which benefit from the robustness of the topological state. However, these devices often operate at excessively high frequencies. To address this issue, this study proposes a novel acoustic energy harvesting device based on the topological edge state of a multi-resonant phononic crystal. By introducing multiple resonant cavities, the device achieves improved robustness and reduced operating frequency. The theoretical model of the device is established and the robustness of the edge states is verified through finite element method (FEM) simulations. The results demonstrate that the device effectively collects acoustic energy, with maximum output voltage observed at an incident frequency of 718 Hz and a maximum voltage amplitude of 132.5 mV. Additionally, even with point defects, the device still demonstrates good acoustic energy collection capability, with a maximum voltage of 96.5 mV at 707 Hz. In conclusion, the topological edge state of a multi-resonant phononic crystal can be designed as an excellent acoustic energy harvesting device due to its lower operating frequency and improved design robustness.
Article
Materials Science, Multidisciplinary
Zhenyu Wang, Houyin Li, Zhennan Wang, Zhenzhen Liu, Jinlong Luo, Jian Huang, Xiaoyan Wang, Rongli Wang, Hai Yang
Summary: The study explores higher-order topological insulators in a two-dimensional square-lattice sonic crystal and confirms the existence of zero-dimensional topological corner states. Acoustic experiments observe that these topological corner states are present at both right-angled and straight-angled corners.
Article
Engineering, Mechanical
Shuowei An, Tuo Liu, Haiyan Fan, He Gao, Zhongming Gu, Shanjun Liang, Sibo Huang, Yi Zheng, Yafeng Chen, Li Cheng, Jie Zhu
Summary: This study proposes a second-order elastic topological insulator (SETI) with valley-selective topological corner states, which can be activated by engineering the valley positions. Experimental results validate the existence of valley-selective corner states and the anti-symmetric displacement profile. This research provides a new approach for the flexible manipulation of elastic waves and has potential applications in various fields.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Physics, Applied
Lin-Lin Lei, Ling-Juan He, Wen-Xing Liu, Qing-Hua Liao, Tian-Bao Yu
Summary: Recently, higher-order topological insulators (HOTIs) have been extended to classical wave systems. We propose a second-order topological phoxonic crystal (PXC) that supports the coexistence of photonic and phononic topological corner states and demonstrates robustness against disorders and defects.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Danwei Liao, Zichong Yue, Zhiwang Zhang, Hai-Xiao Wang, Ying Cheng, Xiaojun Liu
Summary: This study establishes the connection between acoustic Tamm mode and typical topological acoustic mode, and observes the existence and variation of Tamm edge modes and Tamm corner modes through experimental and numerical simulations. The findings are significant for the development of acoustic functional devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Multidisciplinary
Zichong Yue, Zhiwang Zhang, Hai-Xiao Wang, Wei Xiong, Ying Cheng, Xiaojun Liu
Summary: Research on the application of higher-order topological insulators in acoustic systems is highly significant. This study proposes a new design scheme for acoustic SOTIs and observes the state switching process experimentally. The results demonstrate the robustness of topological corner states in the presence of defects.
NEW JOURNAL OF PHYSICS
(2022)
Article
Multidisciplinary Sciences
Zhiwang Zhang, Penglin Gao, Wenjie Liu, Zichong Yue, Ying Cheng, Xiaojun Liu, Johan Christensen
Summary: The authors engineer an artificial honeycomb lattice in single-wall carbon nanotubes and explore their topological features for sound. They find that armchair tubes remain gapless while the zigzag counterparts host nontrivial edge states. The structured tubular lattice symmetry remains intact, and its nontrivial phase is governed by the chirality and the tube diameter. This research has broad implications for various fields such as acoustics, photonics, mechanics, and electronics.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Physical
Rene Pernas-Salomon, Li-Yang Zheng, Zhiwang Zhang, Penglin Gao, Xiaojun Liu, Ying Cheng, Johan Christensen
Summary: This article introduces the research progress in thermoacoustic topological materials, which constructs acoustic lattices coated with electrically biased carbon nanotube films. It investigates the influence of geometry and acoustic gain on acoustic interactions.
NPJ COMPUTATIONAL MATERIALS
(2022)
Review
Multidisciplinary Sciences
Xiujuan Zhang, Farzad Zangeneh-Nejad, Ze-Guo Chen, Ming-Hui Lu, Johan Christensen
Summary: Light and sound are widely studied as classical waves, but they have recently been connected to exotic topological phases of matter. This has sparked a new wave of research, going beyond conventional topological systems and exploring non-linear, non-Hermitian, and non-Abelian topology, as well as topological defects. This article provides an overview of the current state of research and explores future directions for valuable applications.
Article
Nanoscience & Nanotechnology
J. Feilhauer, M. Zelent, Zhiwang Zhang, J. Christensen, M. Mruczkiewicz
Summary: We demonstrate a numerical simulation of magnonic crystals with unidirectional, topologically protected edge states. The crystal is composed of dipolarly coupled Permalloy triangles, and we show that the structure can be scaled up due to its geometry. Edge states can be found over a wide frequency range, and experimental detection can be done using state-of-the-art techniques. We present a proof-of-concept magnonic Chern topological insulator nanostructure with a simple geometry feasible for experimental realization. Additionally, we demonstrate a magnonic switch by inducing a topological phase transition that changes the direction of the topological edge state.
Article
Physics, Applied
Taimin Wang, Chun Gong, Suying Zhang, Yuanzhou Zhu, Houyou Long, Ying Cheng, Xiaojun Liu
Summary: Emerging artificial acoustically soft boundaries (ASBs) have great potential for sound absorptive devices. However, current ASBs have narrow-band limitations that require stringent matching of resonant characteristics. This study proposes a method to construct a broadband ASB (BASB) by coupling two multi-band ASBs using coiled space resonators (CSRs), achieving ultra-broadband absorption.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Chen Liu, Zhiwang Zhang, Danwei Liao, Zichong Yue, Chengrong Ma, Ying Cheng, Xiaojun Liu
Summary: Over the recent decade, topological insulators have become a focus of research in the field of acoustics due to their unique properties for manipulating wave propagation. However, most studies currently are reported in a complex context, and it is still a challenge to achieve efficient acoustic rainbow trapping in a straightforward setup.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Multidisciplinary
Bolun Hu, Zhiwang Zhang, Zichong Yue, Danwei Liao, Yimin Liu, Haixiao Zhang, Ying Cheng, Xiaojun Liu, Johan Christensen
Summary: The Su-Schrieffer-Heeger (SSH) model is a fundamental framework in condensed-matter topology, specifically for studying spinless electrons in chains with staggered bonds. The chiral symmetry of this model ensures the existence of surface states at zero energy within the energy gap. Symmetry plays a crucial role in artificial materials subjected to parity and time-reversal operations. In this study, we introduce the concept of anti-PT (APT) symmetric systems in an acoustic SSH lattice with gain and loss components. Our experiments demonstrate the importance of non-Hermitian phase in the topological defect states, where broken symmetry suppresses them and intact PT or APT symmetry leads to damped or evanescent decay, respectively.
PHYSICAL REVIEW LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Fangfang Ju, Chen Liu, Ying Cheng, Shengyou Qian, Xiaojun Liu
Summary: This study extends parity-time symmetric systems to acoustics by using coupled Mie resonators, achieving PT symmetry with only passive materials. Coherent perfect absorption is observed in the PT symmetric phase, showcasing potential applications in tunable noise control and acoustic modulators.
Article
Materials Science, Multidisciplinary
Maria Rosendo Lopez, Zhiwang Zhang, Daniel Torrent, Johan Christensen
Summary: Rotating overlapping lattices leads to moire interference patterns and correlated superconductivity in twisted bilayer graphene. This study employs a sound wave expansion technique to mimic this physics and designs moire sound interference characteristics in holey bilayer plates.
COMMUNICATIONS MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Penglin Gao, Yegao Qu, Johan Christensen
Summary: This research has identified stable unidirectional Rayleigh surface waves in active materials, which exhibit non-reciprocal and non-Hermitian characteristics, unlike waves in passive solids. These findings may open up new possibilities for manipulating elastic waves in unconventional ways.
COMMUNICATIONS MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Danwei Liao, Zhiwang Zhang, Ying Cheng, Xiaojun Liu
Summary: This study proposes a subwavelength acoustic third-order topological insulator based on the theoretical framework of acoustic transmission lines, which enables the engineering of acoustic negative couplings to achieve topological corner states. The occurrence of these states in both the 3D Su-Schrieffer-Heeger (SSH) model and the octupole insulator is validated through topological invariant calculations and numerical simulations in analogous acoustic networks.
