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Liu YW, Zhuang YC, Ren YN, Yan C, Zhou XF, Yang Q, Sun QF, He L. Visualizing a single wavefront dislocation induced by orbital angular momentum in graphene. Nat Commun 2024; 15:3546. [PMID: 38670960 PMCID: PMC11053005 DOI: 10.1038/s41467-024-47756-w] [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: 01/17/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
Phase singularities are phase-indeterminate points where wave amplitudes are zero, which manifest as phase vertices or wavefront dislocations. In the realm of optical and electron beams, the phase singularity has been extensively explored, demonstrating a profound connection to orbital angular momentum. Direct local imaging of the impact of orbital angular momentum on phase singularities at the nanoscale, however, remains challenging. Here, we study the role of orbital angular momentum in phase singularities in graphene, particularly at the atomic level, through scanning tunneling microscopy and spectroscopy. Our experiments demonstrate that the scatterings between different orbital angular momentum states, which are induced by local rotational symmetry-breaking potentials, can generate additional phase singularities, and result in robust single-wavefront dislocations in real space. Our results pave the way for exploring the effects of orbital degree of freedom on quantum phases in quasiparticle interference processes.
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Affiliation(s)
- Yi-Wen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Yu-Chen Zhuang
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
| | - Ya-Ning Ren
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Chao Yan
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Xiao-Feng Zhou
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Qian Yang
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China
| | - Qing-Feng Sun
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
- Hefei National Laboratory, Hefei, 230088, China.
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, China.
- Key Laboratory of Multiscale Spin Physics, Ministry of Education, 100875, Beijing, China.
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Ren M, Yu Y, Wu B, Qi X, Wang Y, Yao X, Ren J, Guo Z, Jiang H, Chen H, Liu XJ, Chen Z, Sun Y. Realization of Gapped and Ungapped Photonic Topological Anderson Insulators. PHYSICAL REVIEW LETTERS 2024; 132:066602. [PMID: 38394559 DOI: 10.1103/physrevlett.132.066602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 01/03/2024] [Indexed: 02/25/2024]
Abstract
It is commonly believed that topologically nontrivial one-dimensional systems support edge states rather than bulk states at zero energy. In this work, we find an unanticipated case of topological Anderson insulator (TAI) phase where two bulk modes are degenerate at zero energy, in addition to degenerate edge modes. We term this "ungapped TAI" to distinguish it from the previously known gapped TAIs. Our experimental realization of both gapped and ungapped TAIs relies on coupled photonic resonators, in which the disorder in coupling is judiciously engineered by adjusting the spacing between the resonators. By measuring the local density of states both in the bulk and at the edges, we demonstrate the existence of these two types of TAIs, together forming a TAI plateau in the phase diagram. Our experimental findings are well supported by theoretical analysis. In the ungapped TAI phase, we observe stable coexistence of topological edge states and localized bulk states at zero energy, highlighting the distinction between TAIs and traditional topological insulators.
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Affiliation(s)
- Mina Ren
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Ye Yu
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Bintao Wu
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Xin Qi
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Yiwei Wang
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Xiaogang Yao
- Information Materials and Devices Research Center, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 201800, China
| | - Jie Ren
- Center for Phononics and Thermal Energy Science, China-EU Joint Lab on Nanophononics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhiwei Guo
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Haitao Jiang
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Hong Chen
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Xiong-Jun Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- International Quantum Academy, Shenzhen 518048, China
| | - Zhigang Chen
- MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China
| | - Yong Sun
- MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
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A Third Angular Momentum of Photons. Symmetry (Basel) 2023. [DOI: 10.3390/sym15010158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Photons that acquire orbital angular momentum move in a helical path and are observed as a light ring. During helical motion, if a force is applied perpendicular to the direction of motion, an additional radial angular momentum is introduced, and alternate dark spots appear on the light ring. Here, a third, centrifugal angular momentum has been added by twisting the helical path further according to the three-step hierarchical assembly of helical organic nanowires. Attaining a third angular momentum is the theoretical limit for a photon. The additional angular momentum converts the dimensionless photon to a hollow spherical photon condensate with interactive dark regions. A stream of these photon condensates can interfere like a wave or disintegrate like matter, similar to the behavior of electrons.
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