1
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Li Z, Wang LW, Wang X, Lin ZK, Ma G, Jiang JH. Observation of dynamic non-Hermitian skin effects. Nat Commun 2024; 15:6544. [PMID: 39095338 PMCID: PMC11297047 DOI: 10.1038/s41467-024-50776-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2023] [Accepted: 07/19/2024] [Indexed: 08/04/2024] Open
Abstract
Non-Hermitian physics has emerged as a new paradigm that profoundly changes our understanding of non-equilibrium systems, introducing novel concepts such as exceptional points, spectral topology, and non-Hermitian skin effects (NHSEs). Most existing studies focus on non-Hermitian eigenstates, whereas dynamic properties have been discussed only recently, and the dynamic NHSEs are not yet confirmed in experiments. Here, we report the experimental observation of non-Hermitian skin dynamics using tunable one-dimensional nonreciprocal double-chain mechanical systems with glide-time symmetry. Remarkably, dynamic NHSEs are observed with various behaviors in different dynamic phases, which can be understood via the generalized Brillouin zone and the related concepts. Moreover, the observed dynamic NHSEs, amplifications, bulk unidirectional wave propagation, and boundary wave trapping provide promising ways to manipulate waves in a controllable and robust way. Our findings open a new pathway toward non-Hermitian dynamics, which will fertilize the study of non-equilibrium phases of matter.
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Affiliation(s)
- Zhen Li
- Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
| | - Li-Wei Wang
- School of Physical Science and Technology, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, China
- School of Biomedical Engineering, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
- Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou, China
| | - Xulong Wang
- Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
| | - Zhi-Kang Lin
- School of Physical Science and Technology, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, China
| | - Guancong Ma
- Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.
- Shenzhen Institute for Research and Continuing Education, Hong Kong Baptist University, Shenzhen, 518000, China.
| | - Jian-Hua Jiang
- School of Physical Science and Technology, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, China.
- School of Biomedical Engineering, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China.
- Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou, China.
- Department of Modern Physics, School of Physical Sciences, University of Science and Technology of China, Hefei, China.
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2
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Xue P, Lin Q, Wang K, Xiao L, Longhi S, Yi W. Self acceleration from spectral geometry in dissipative quantum-walk dynamics. Nat Commun 2024; 15:4381. [PMID: 38782911 PMCID: PMC11116542 DOI: 10.1038/s41467-024-48815-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 05/10/2024] [Indexed: 05/25/2024] Open
Abstract
The dynamic behavior of a physical system often originates from its spectral properties. In open systems, where the effective non-Hermitian description enables a wealth of spectral structures in the complex plane, the concomitant dynamics are significantly enriched, whereas the identification and comprehension of the underlying connections are challenging. Here we experimentally demonstrate the correspondence between the transient self-acceleration of local excitations and the non-Hermitian spectral topology using lossy photonic quantum walks. Focusing first on one-dimensional quantum walks, we show that the measured short-time acceleration of the wave function is proportional to the area enclosed by the eigenspectrum. We then reveal a similar correspondence in two-dimension quantum walks, where the self-acceleration is proportional to the volume enclosed by the eigenspectrum in the complex parameter space. In both dimensions, the transient self-acceleration crosses over to a long-time behavior dominated by a constant flow at the drift velocity. Our results unveil the universal correspondence between spectral topology and transient dynamics, and offer a sensitive probe for phenomena in non-Hermitian systems that originate from spectral geometry.
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Affiliation(s)
- Peng Xue
- School of Physics, Southeast University, Nanjing, 211189, China.
| | - Quan Lin
- School of Physics, Southeast University, Nanjing, 211189, China
| | - Kunkun Wang
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei, 230601, China
| | - Lei Xiao
- School of Physics, Southeast University, Nanjing, 211189, China
| | - Stefano Longhi
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, Milano, I-20133, Italy.
- IFISC (UIB-CSIC) Instituto de Fisica Interdisciplinar y Sistemas Complejos, Palma de Mallorca, E-07122, Spain.
| | - Wei Yi
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, 230026, China.
- CAS Center For Excellence in Quantum Information and Quantum Physics, Hefei, 230026, China.
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3
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Zhu J, Mao YL, Chen H, Yang KX, Li L, Yang B, Li ZD, Fan J. Observation of Non-Hermitian Edge Burst Effect in One-Dimensional Photonic Quantum Walk. PHYSICAL REVIEW LETTERS 2024; 132:203801. [PMID: 38829094 DOI: 10.1103/physrevlett.132.203801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 04/19/2024] [Indexed: 06/05/2024]
Abstract
Non-Hermitian systems can exhibit unique quantum phases without any Hermitian counterparts. For example, the latest theoretical studies predict a new surprising phenomenon that bulk bands can localize and dissipate prominently at the system boundary, which is dubbed the non-Hermitian edge burst effect. Here we realize a one-dimensional non-Hermitian Su-Schrieffer-Heeger lattice with bulk translation symmetry implemented with a photonic quantum walk. Employing time-resolved single-photon detection to characterize the chiral motion and boundary localization of bulk bands, we determine experimentally that the dynamics underlying the non-Hermitian edge burst effect is due to the interplay of non-Hermitian skin effect and imaginary band gap closing. This new non-Hermitian physical effect deepens our understanding of quantum dynamics in open quantum systems.
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Affiliation(s)
- Jiankun Zhu
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Ya-Li Mao
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Hu Chen
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Kui-Xing Yang
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Linhu Li
- Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing and School of Physics and Astronomy, Sun Yat-Sen University (Zhuhai Campus), Zhuhai 519082, China
| | - Bing Yang
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Zheng-Da Li
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jingyun Fan
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- Center for Advanced Light Source, Southern University of Science and Technology, Shenzhen 518055, China
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4
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Longhi S. Incoherent non-Hermitian skin effect in photonic quantum walks. LIGHT, SCIENCE & APPLICATIONS 2024; 13:95. [PMID: 38658541 PMCID: PMC11043335 DOI: 10.1038/s41377-024-01438-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/08/2024] [Accepted: 03/25/2024] [Indexed: 04/26/2024]
Abstract
The non-Hermitian skin effect describes the concentration of an extensive number of eigenstates near the boundaries of certain dissipative systems. This phenomenon has raised a huge interest in different areas of physics, including photonics, deeply expanding our understanding of non-Hermitian systems and opening up new avenues in both fundamental and applied aspects of topological phenomena. The skin effect has been associated to a nontrivial point-gap spectral topology and has been experimentally demonstrated in a variety of synthetic matter systems, including photonic lattices. In most of physical models exhibiting the non-Hermitian skin effect full or partial wave coherence is generally assumed. Here we push the concept of skin effect into the fully incoherent regime and show that rather generally (but not universally) the non-Hermitian skin effect persists under dephasing dynamics. The results are illustrated by considering incoherent light dynamics in non-Hermitian photonic quantum walks.
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Affiliation(s)
- Stefano Longhi
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133, Milano, Italy.
- IFISC (UIB-CSIC), Instituto de Fisica Interdisciplinar y Sistemas Complejos, E-07122, Palma de Mallorca, Spain.
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5
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Zhang X, Wu C, Yan M, Liu N, Wang Z, Chen G. Observation of continuum Landau modes in non-Hermitian electric circuits. Nat Commun 2024; 15:1798. [PMID: 38413597 PMCID: PMC10899205 DOI: 10.1038/s41467-024-46122-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Accepted: 02/08/2024] [Indexed: 02/29/2024] Open
Abstract
Continuum Landau modes - predicted recently in a non-Hermitian Dirac Hamiltonian under a uniform magnetic field - are continuous bound states with no counterparts in Hermitian systems. However, they have still not been confirmed in experiments. Here, we report an experimental observation of continuum Landau modes in non-Hermitian electric circuits, in which the non-Hermitian Dirac Hamiltonian is simulated by non-reciprocal hoppings and the pseudomagnetic field is introduced by inhomogeneous complex on-site potentials. Through measuring the admittance spectrum and the eigenstates, we successfully verify key features of continuum Landau modes. Particularly, we observe the exotic voltage response acting as a rainbow trap or wave funnel through full-field excitation. This response originates from the linear relationship between the modes' center position and complex eigenvalues. Our work builds a bridge between non-Hermiticity and magnetic fields, and thus opens an avenue to explore exotic non-Hermitian physics.
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Affiliation(s)
- Xuewei Zhang
- School of Physics and Microelectronics, Key Laboratory of Materials Physics of Ministry of Education, Zhengzhou University, Zhengzhou, 450001, China
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan, 030006, China
| | - Chaohua Wu
- School of Physics and Microelectronics, Key Laboratory of Materials Physics of Ministry of Education, Zhengzhou University, Zhengzhou, 450001, China
| | - Mou Yan
- School of Physics and Microelectronics, Key Laboratory of Materials Physics of Ministry of Education, Zhengzhou University, Zhengzhou, 450001, China
- Institute of Quantum Materials and Physics, Henan Academy of Sciences, Zhengzhou, 450046, China
| | - Ni Liu
- Institute of Theoretical Physics, Shanxi University, Taiyuan, 030006, China
| | - Ziyu Wang
- The Institute of Technological Sciences, Wuhan University, Wuhan, 430072, China.
| | - Gang Chen
- School of Physics and Microelectronics, Key Laboratory of Materials Physics of Ministry of Education, Zhengzhou University, Zhengzhou, 450001, China.
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser spectroscopy, Shanxi University, Taiyuan, 030006, China.
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6
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Wang X, Hao R, Fan P, Hu L, Ye B, Zou Y, Jin S. Effective enhancement of the non-Hermitian corner skin effect in reciprocal photonic crystals. OPTICS LETTERS 2024; 49:554-557. [PMID: 38300057 DOI: 10.1364/ol.513800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 01/01/2024] [Indexed: 02/02/2024]
Abstract
With the rich physical phenomena arising from non-Hermitian systems, the non-Hermitian skin effect (NHSE) has become a current research hotspot. Nowadays, the corner skin effect based on non-reciprocal photonic crystals has been proposed. Considering the complexity of realizing non-reciprocity, the corner skin effect based on reciprocal photonic crystals is well worth investigating. In this Letter, a non-Hermitian reciprocal geometry-dependent corner skin effect based on two-dimensional photonic crystals is presented, which is manifested as the distribution of eigenstates on the corners of a particular geometry by applying open boundary conditions in both directions of photonic crystals. For the better application of the NHSE in the future, such as highly sensitive sensors and lasers, a new, to the best of our knowledge, method that can effectively enhance the performance of the NHSE in photonic crystals is proposed. The method introduces both gain and loss in an ideal photonic crystal to enhance the non-Hermitian specificity of the system, which improves the performance of the non-Hermitian corner skin effect of photonic crystals by 64.5%. Furthermore, this geometry-dependent corner skin effect is corroborated with the spectral topology.
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7
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Lin Q, Yi W, Xue P. Manipulating directional flow in a two-dimensional photonic quantum walk under a synthetic magnetic field. Nat Commun 2023; 14:6283. [PMID: 37805651 PMCID: PMC10560269 DOI: 10.1038/s41467-023-42045-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 09/28/2023] [Indexed: 10/09/2023] Open
Abstract
Matter transport is a fundamental process in nature. Understanding and manipulating flow in a synthetic media often have rich implications for modern device design. Here we experimentally demonstrate directional transport of photons in a two-dimensional quantum walk, where the light propagation is highly tunable through dissipation and synthetic magnetic flux. The directional flow hereof underlies the emergence of the non-Hermitian skin effect, with its orientation continuously adjustable through the photon-loss parameters. By contrast, the synthetic magnetic flux originates from an engineered geometric phase, which, by inducing localized cyclotron orbits, suppresses the bulk flow through magnetic confinement. We further demonstrate how the directional flow and synthetic flux impact the dynamics of the Floquet topological edge modes along an engineered boundary. Our results exemplify an intriguing strategy for engineering directed light transport, highlighting the interplay of non-Hermiticity and gauge fields in synthetic systems of higher dimensions.
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Affiliation(s)
- Quan Lin
- Beijing Computational Science Research Center, 100084, Beijing, China
| | - Wei Yi
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, 230026, Hefei, China.
- CAS Center For Excellence in Quantum Information and Quantum Physics, 230026, Hefei, China.
| | - Peng Xue
- Beijing Computational Science Research Center, 100084, Beijing, China.
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8
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Chen C, Liu RZ, Wu J, Su ZE, Ding X, Qin J, Wang L, Zhang WW, He Y, Wang XL, Lu CY, Li L, Sanders BC, Liu XJ, Pan JW. Berry Curvature and Bulk-Boundary Correspondence from Transport Measurement for Photonic Chern Bands. PHYSICAL REVIEW LETTERS 2023; 131:133601. [PMID: 37831993 DOI: 10.1103/physrevlett.131.133601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 08/17/2023] [Indexed: 10/15/2023]
Abstract
Berry curvature is a fundamental element to characterize topological quantum physics, while a full measurement of Berry curvature in momentum space was not reported for topological states. Here we achieve two-dimensional Berry curvature reconstruction in a photonic quantum anomalous Hall system via Hall transport measurement of a momentum-resolved wave packet. Integrating measured Berry curvature over the two-dimensional Brillouin zone, we obtain Chern numbers corresponding to -1 and 0. Further, we identify bulk-boundary correspondence by measuring topology-linked chiral edge states at the boundary. The full topological characterization of photonic Chern bands from Berry curvature, Chern number, and edge transport measurements enables our photonic system to serve as a versatile platform for further in-depth study of novel topological physics.
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Affiliation(s)
- Chao Chen
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Run-Ze Liu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Jizhou Wu
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Zu-En Su
- The Physics Department and the Solid State Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Xing Ding
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Jian Qin
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Lin Wang
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - Wei-Wei Zhang
- School of Computer Science, Northwestern Polytechnical University, Xi'an 710129, China
| | - Yu He
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xi-Lin Wang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Chao-Yang Lu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Li Li
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Barry C Sanders
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
- Institute for Quantum Science and Technology, University of Calgary, Alberta T2N 1N4, Canada
| | - Xiong-Jun Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- International Quantum Academy, Shenzhen 518048, China
| | - Jian-Wei Pan
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China
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9
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Jiang H, Lee CH. Dimensional Transmutation from Non-Hermiticity. PHYSICAL REVIEW LETTERS 2023; 131:076401. [PMID: 37656848 DOI: 10.1103/physrevlett.131.076401] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 03/18/2023] [Accepted: 07/25/2023] [Indexed: 09/03/2023]
Abstract
Dimensionality plays a fundamental role in the classification of novel phases and their responses. In generic lattices of 2D and beyond, however, we found that non-Hermitian couplings do not merely distort the Brillouin zone (BZ), but can in fact alter its effective dimensionality. This is due to the fundamental noncommutativity of multidimensional non-Hermitian pumping, which obstructs the usual formation of a generalized complex BZ. As such, basis states are forced to assume "entangled" profiles that are orthogonal in a lower dimensional effective BZ, completely divorced from any vestige of lattice Bloch states unlike conventional skin states. Characterizing this reduced dimensionality is an emergent winding number intimately related to the homotopy of noncontractible spectral paths. We illustrate this dimensional transmutation through a 2D model whose topological zero modes are protected by a 1D, not 2D, topological invariant. Our findings can be readily demonstrated via the bulk properties of nonreciprocally coupled platforms such as circuit arrays, and provokes us to rethink the fundamental role of geometric obstruction in the dimensional classification of topological states.
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Affiliation(s)
- Hui Jiang
- Department of Physics, National University of Singapore, Singapore 117551, Republic of Singapore
| | - Ching Hua Lee
- Department of Physics, National University of Singapore, Singapore 117551, Republic of Singapore
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, China
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10
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Zhang K, Fang C, Yang Z. Dynamical Degeneracy Splitting and Directional Invisibility in Non-Hermitian Systems. PHYSICAL REVIEW LETTERS 2023; 131:036402. [PMID: 37540867 DOI: 10.1103/physrevlett.131.036402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 02/28/2023] [Accepted: 06/21/2023] [Indexed: 08/06/2023]
Abstract
In this Letter, we introduce the concept of dynamical degeneracy splitting to describe the anisotropic decay behaviors in non-Hermitian systems. We demonstrate that systems with dynamical degeneracy splitting exhibit two distinctive features: (i) the system shows frequency-resolved non-Hermitian skin effect; (ii) Green's function exhibits anomalous behavior at given frequency, leading to uneven broadening in spectral function and anomalous scattering. As an application, we propose directional invisibility based on wave packet dynamics to investigate the geometry-dependent skin effect in higher dimensions. Our work elucidates a faithful correspondence between non-Hermitian skin effect and Green's function, offering a guiding principle for exploration of novel physical phenomena emerging from this effect.
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Affiliation(s)
- Kai Zhang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Chen Fang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- Kavli Institute for Theoretical Sciences, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhesen Yang
- Kavli Institute for Theoretical Sciences, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, Xiamen University, Xiamen 361005, Fujian Province, China
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11
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Wan LL, Lü XY. Quantum-Squeezing-Induced Point-Gap Topology and Skin Effect. PHYSICAL REVIEW LETTERS 2023; 130:203605. [PMID: 37267552 DOI: 10.1103/physrevlett.130.203605] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 04/21/2023] [Indexed: 06/04/2023]
Abstract
We theoretically predict the squeezing-induced point-gap topology together with a symmetry-protected Z_{2} "skin effect" in a one-dimensional (1D) quadratic-bosonic system. Protected by a time-reversal symmetry, such a topology is associated with a novel Z_{2} invariant (similar to quantum spin-Hall insulators), which is fully capable of characterizing the occurrence of the Z_{2} skin effect. Focusing on zero energy, the parameter regime of this skin effect in the phase diagram just corresponds to a "real- and point-gap coexisting topological phase." Moreover, this phase associated with the symmetry-protected Z_{2} skin effect is experimentally observable by detecting the steady-state power spectral density. Our Letter is of fundamental interest in enriching non-Bloch topological physics by introducing quantum squeezing and has potential applications for the engineering of symmetry-protected sensors based on the Z_{2} skin effect.
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Affiliation(s)
- Liang-Liang Wan
- School of Physics and Institute for Quantum Science and Engineering, Huzhong University of Science and Technology, Wuhan 430074, China and Wuhan Institute of Quantum Technology, Wuhan 430074, China
| | - Xin-You Lü
- School of Physics and Institute for Quantum Science and Engineering, Huzhong University of Science and Technology, Wuhan 430074, China and Wuhan Institute of Quantum Technology, Wuhan 430074, China
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12
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Abstract
The discovery of non-Hermitian skin effect (NHSE) has opened an exciting direction for unveiling unusual physics and phenomena in non-Hermitian system. Despite notable theoretical breakthroughs, actual observation of NHSE's whole evolvement, however, relies mainly on gain medium to provide amplified mode. It typically impedes the development of simple, robust system. Here, we show that a passive system is fully capable of supporting the observation of the complete evolution picture of NHSE, without the need of any gain medium. With a simple lattice model and acoustic ring resonators, we use complex-frequency excitation to create virtual gain effect, and experimentally demonstrate that exact NHSE can persist in a totally passive system during a quasi-stationary stage. This results in the transient NHSE: passive construction of NHSE in a short time window. Despite the general energy decay, the localization character of skin modes can still be clearly witnessed and successfully exploited. Our findings unveil the importance of excitation in realizing NHSE and paves the way towards studying the peculiar features of non-Hermitian physics with diverse passive platforms.
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13
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Wang HY, Zhao XM, Zhuang L, Liu WM. Non-Floquet engineering in periodically driven dissipative open quantum systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:365402. [PMID: 35760065 DOI: 10.1088/1361-648x/ac7c4e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
Floquet engineering plays a key role in realizing novel dynamical topological states. The conventional Floquet engineering, however, only applies to time-periodic non-dissipative Hermitian systems, and for the open quantum systems, non-Hermitian processes usually occur. So far, it remains unclear how to characterize the topological phases of time-periodic open quantum systems via the frequency space Floquet Hamiltonian. Here, we propose the non-Floquet theory to solve the problem and illustrate it by a continuously time-periodic non-Hermitian bipartite chain. In non-Floquet theory, a temporal non-unitary transformation is exercised on the Floquet states, and the transformed Floquet spectrum restores the form of the Wannier-Stark ladder. Besides, we also show that different choices of the starting points of the driving period can result in different localization behavior, effects of which can reversely be utilized to design quantum detectors of phases in dissipative oscillating fields. Our methods are capable of describing topological features in dynamical open quantum systems with various driving types and can find its applications to construct new types of dynamical topological materials.
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Affiliation(s)
- Huan-Yu Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Xiao-Ming Zhao
- Department of Physics, Institute of Theoretical physics, University of Science and Technology Beijing, Beijing, 100083, People's Republic of China
| | - Lin Zhuang
- School of Physics, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China
| | - Wu-Ming Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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14
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Longhi S. Selective and tunable excitation of topological non-Hermitian quasi-edge modes. Proc Math Phys Eng Sci 2022. [DOI: 10.1098/rspa.2021.0927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Non-Hermitian lattices under semi-infinite boundary conditions sustain an extensive number of exponentially localized states, dubbed non-Hermitian quasi-edge modes. Quasi-edge states arise rather generally in systems displaying the non-Hermitian skin effect and can be predicted from the non-trivial topology of the energy spectrum under periodic boundary conditions via a bulk-edge correspondence. However, the selective excitation of the system in one among the infinitely many topological quasi-edge states is challenging both from practical and conceptual viewpoints. In fact, in any realistic system with a finite lattice size most of the quasi-edge states collapse and become metastable states. Here we suggest a route toward the selective and tunable excitation of topological quasi-edge states that avoids the collapse problem by emulating semi-infinite lattice boundaries via tailored on-site potentials at the edges of a finite lattice. We illustrate such a strategy by considering a non-Hermitian topological interface obtained by connecting two Hatano–Nelson chains with opposite imaginary gauge fields, which is amenable for a full analytical treatment.
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Affiliation(s)
- Stefano Longhi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy
- IFISC (UIB-CSIC), Instituto de Fisica Interdisciplinar y Sistemas Complejos, Palma de Mallorca 07122, Spain
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