Article
Physics, Multidisciplinary
Haiping Hu, Erhai Zhao
Summary: This study explores knots tied by eigenenergy strings in one-dimensional non-Hermitian Hamiltonians, as well as their relationship with Wilson loops. An algorithm is developed to construct corresponding tight-binding non-Hermitian Hamiltonians and a scheme is proposed to probe knot structures via quantum quench.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Weiyuan Tang, Kun Ding, Guancong Ma
Summary: In this study, non-Abelian state permutations are experimentally demonstrated in a non-Hermitian system. The eigenstates in this system can evolve across different manifolds, corresponding to state permutation. By encircling exceptional arcs, five non-trivial permutations are achieved, indicating the existence of non-Abelian groups in non-Hermitian systems.
NATIONAL SCIENCE REVIEW
(2022)
Article
Physics, Multidisciplinary
Jas Bensa, Marko Znidaric
Summary: This study investigates the rate of producing bipartite entanglement in random quantum circuits and finds that non-Hermiticity can cause different rates than predicted. By studying phase transitions in local relaxation rates, the optimal gates and protocols for generating entanglement at the fastest rate theoretically are identified.
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
Materials Science, Multidisciplinary
Yang Cao, Yang Li, Xiaosen Yang
Summary: The paper investigates a one-dimensional non-Hermitian Su-Schrieffer-Heeger model and identifies the non-Hermitian skin effect. By defining non-Bloch winding numbers, the non-Hermitian bulk-boundary correspondence is successfully established. Even in cases of trivial topology, robust edge states can emerge in the system.
Article
Materials Science, Multidisciplinary
Haiyan Fan, He Gao, Tuo Liu, Shuowei An, Xianghong Kong, Guoqiang Xu, Jie Zhu, Cheng-Wei Qiu, Zhongqing Su
Summary: Non-Hermiticity in acoustic crystals leads to exotic topological phenomena and allows for manipulation of topological modes. Our work demonstrates an acoustic quadrupole topological insulator, offering a reconfigurable and versatile approach to manipulating topological phenomena.
Article
Physics, Applied
S. Puri, J. Ferdous, A. Shakeri, A. Basiri, M. Dubois, H. Ramezani
Summary: Researchers have proposed and tested a non-Hermitian acoustic superlattice that functions as a tunable precise filter, where the second sublattice's properties can be adjusted to absorb or reflect multiple frequencies with high accuracy.
PHYSICAL REVIEW APPLIED
(2021)
Article
Multidisciplinary Sciences
Li Zhang, Yihao Yang, Yong Ge, Yi-Jun Guan, Qiaolu Chen, Qinghui Yan, Fujia Chen, Rui Xi, Yuanzhen Li, Ding Jia, Shou-Qi Yuan, Hong-Xiang Sun, Hongsheng Chen, Baile Zhang
Summary: The experimental realization of the non-Hermitian skin effect in a one-dimensional non-reciprocal acoustic crystal demonstrates unique features such as bipolar localization and Bloch point, revealing previously unnoticed characteristics of NHSE originating from complex non-Hermitian winding topology.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Selma Franca, Viktor Koenye, Fabian Hassler, Jeroen van den Brink, Cosma Fulga
Summary: This study introduces a novel approach to exploring non-Hermitian physics involving reflection from the boundary of insulators, without the need for gain or loss. For strong topological insulators, the reflected waves exhibit non-Hermitian characteristics due to a reflection matrix exhibiting the non-Hermitian skin effect. This research expands the range of experimental platforms that can observe features associated with non-Hermitian topology.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
X. M. Yang, Z. Song
Summary: This work studies the dynamic transition from a trivial insulating state to an ?I-pairing state in a composite non-Hermitian Hubbard system. It is found that the transition occurs by the probability flow from subsystem A to B. The speed of relaxation of the off-diagonal long-range order pair state depends on the order of the exceptional point (EP), while the fidelity of the scheme is immune to the irregularity of the lattice.
Article
Chemistry, Multidisciplinary
Fang Li, Hui Zhang, You Li, Yibin Zhao, Mingyan Liu, Yunwei Yang, Jiamin Yao, Shaolong Min, Erjun Kan, Yi Wan
Summary: Modulating valley pseudospin with interface engineering is crucial for the fabrication of conceptual devices in microelectronics.
Article
Physics, Multidisciplinary
Stefano Longhi
Summary: The Hartman effect refers to the phenomenon that the time taken for a quantum mechanical particle or photon to tunnel through an opaque potential barrier becomes independent of the barrier width for long barriers. It has been observed in various physical settings and sparked debates and controversies regarding the definition and interpretation of tunneling times and the apparent superluminal transmission. This study investigates whether the Hartman effect persists in non-Hermitian barriers under conditions of inelastic scattering.
ANNALEN DER PHYSIK
(2022)
Article
Multidisciplinary Sciences
Sheng Wang, Seokjae Yoo, Sihan Zhao, Wenyu Zhao, Salman Kahn, Dingzhou Cui, Fanqi Wu, Lili Jiang, M. Iqbal Bakti Utama, Hongyuan Li, Shaowei Li, Alexander Zibrov, Emma Regan, Danqing Wang, Zuocheng Zhang, Kenji Watanabe, Takashi Taniguchi, Chongwu Zhou, Feng Wang
Summary: Surface plasmons in mixed-dimensional heterostructures can be highly modulated with electrostatic gating, possibly due to plasmon hybridization. The ability to modulate plasmon wavelengths and retain high figures of merit in the 1D-2D heterostructure suggests potential for diverse designs of tunable plasmonic nanodevices.
NATURE COMMUNICATIONS
(2021)
Editorial Material
Physics, Multidisciplinary
Boxue Zhang, Qingya Li, Xiao Zhang, Ching Hua Lee
Summary: In this study, we investigate the alternative approach provided by the non-Hermitian skin effect for achieving real spectra and system stability. We showcase various ansatz models that do not have obvious symmetry but can possess real spectra for different classes of energy dispersions. These minimal local models can be quickly implemented in non-reciprocal experimental setups such as electrical circuits with operational amplifiers.
Review
Nanoscience & Nanotechnology
Midya Parto, Yuzhou G. N. Liu, Babak Bahari, Mercedeh Khajavikhan, Demetrios N. Christodoulides
Summary: In recent years, concepts from non-Hermitian physics have been successfully deployed in optics and other fields, leading to the discovery of counterintuitive phenomena. These ideas have extended to other areas in search of new behaviors and functionalities that would have been impossible in standard Hermitian arrangements.
Article
Materials Science, Multidisciplinary
Li-Yang Zheng, Xiu-Juan Zhang, Ming-Hui Lu, Yan-Feng Chen, Johan Christensen
Summary: Cutting-edge research has led to the discovery of a new class of topological materials in three-dimensional semimetallic crystals, nodal-line semimetals exhibit robust band-touching manifolds and exotic transport properties. The use of sonic crystals, such as designing a lattice of guiding channels, allows for the mapping of topological characteristics to audible sound properties, demonstrating interesting features like linear crossings and directional sound beams.
MATERIALS TODAY PHYSICS
(2021)
Article
Physics, Applied
M. Mallejac, A. Merkel, J. Sanchez-Dehesa, J. Christensen, V. Tournat, V. Romero-Garcia, J. -P. Groby
Summary: This paper investigates the feasibility of cloaking obstacles using Plate-type Acoustic Metamaterials (PAMs) and presents two distinct strategies for achieving hiding configuration. The study focuses on dealing with unavoidable losses in the system and reports on the analytical, numerical, and experimental findings of a hiding zone. The comparison between cloaking and hiding configurations highlights the difference in scattering properties and the impact of obstacles on the hiding device.
JOURNAL OF APPLIED PHYSICS
(2021)
Editorial Material
Nanoscience & Nanotechnology
Penglin Gao, Johan Christensen
Summary: Localized zero-energy fermionic states can bind to topological defects like two-dimensional vortices, which can be found in the bulk of artificial acoustic and optical lattices.
NATURE NANOTECHNOLOGY
(2021)
Article
Multidisciplinary Sciences
Bolun Hu, Zhiwang Zhang, Haixiao Zhang, Liyang Zheng, Wei Xiong, Zichong Yue, Xiaoyu Wang, Jianyi Xu, Ying Cheng, Xiaojun Liu, Johan Christensen
Summary: The study focuses on the application of sound waves in non-Hermitian systems and the importance of topological insulators in sound and light guidance. By using carbon nanotube films for acoustic gain, a topological gallery insulator has been successfully constructed, allowing for amplified and focused sound at audible frequencies.
Article
Physics, Multidisciplinary
Li-Yang Zheng, Johan Christensen
Summary: The study demonstrates an acoustic 3D honeycomb lattice featuring several Dirac cones, leading to different orders of topological insulator properties. By analyzing the topological origin of surface, hinge, and corner states, new routes for controlling sound and vibration are offered.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Jingjing Liu, Zhengwei Li, Yujiang Ding, An Chen, Bin Liang, Jing Yang, Jian-Chun Cheng, Johan Christensen
Summary: This article introduces an ultrasonic motor based on a meta engine block that can convert the linear momentum of sound into orbital angular momentum. By optimizing the design and adjusting the boundary conditions, efficient excitation of the desired angular momentum is achieved, enabling noninvasive driving of the ultrasonic motor.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Yurou Jia, Yimin Liu, Bolun Hu, Wei Xiong, Yechao Bai, Ying Cheng, Dajian Wu, Xiaojun Liu, Johan Christensen
Summary: Multiplexing technology plays a crucial role in acoustic communication, and this study introduces a hybrid mode-frequency-division multiplexer on an acoustic metasurface decorated with carbon nanotube patches. By changing the azimuthal phase distribution, flexible combinations of OAM modes with diverse frequency shifts can be obtained, significantly increasing the communication capacity.
ADVANCED MATERIALS
(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
Physics, Applied
Jinjie Shi, Chenkai Liu, Chang Guo, Hongchen Chu, Xiaozhou Liu, Johan Christensen, Yun Lai
Summary: This study theoretically proposes and experimentally demonstrates acoustic metasurfaces called acoustic metaveils, which can achieve undistorted transmission and configurable reflection, providing remarkable camouflage effects for sonars. The metaveils are composed of configurable arrays of two acoustic meta-atoms, and the reflection can be conveniently manipulated by changing the arrangement.
PHYSICAL REVIEW APPLIED
(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, 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
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)
