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Weyl points-topological monopoles of quantized Berry flux-are predicted to spread to Weyl exceptional rings in the presence of non-Hermiticity. Here, we use a one-dimensional Aubry-Andre-Harper model to construct a Weyl semimetal in a three-dimensional parameter space comprising one reciprocal dimension and two synthetic dimensions. The inclusion of non-Hermiticity in the form of gain and loss produces a synthetic Weyl exceptional ring (SWER). The topology of the SWER is characterized by both its topological charge and non-Hermitian winding numbers. We experimentally observe the SWER and synthetic Fermi arc in a one-dimensional phononic crystal with the non-Hermiticity introduced by active acoustic components. Our findings pave the way for studying the high-dimensional non-Hermitian topological physics in acoustics.
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http://dx.doi.org/10.1103/PhysRevLett.129.084301 | DOI Listing |
J Phys Condens Matter
September 2025
Department of Physics, University of Calcutta, 92 A P C Road, Kolkata 700009, India.
The discovery of magnetic Weyl semimetals (WSMs) has drawn significant interest due to their exceptional topological properties and anomalous transport behaviors, presenting exciting possibilities for advanced technological applications. Co-based Heusler compounds, with their unique band structures, have emerged as key materials for exploring the interplay between magnetism and topology. In this work, we perform a detailed first-principles study on Co2-xCrMnGe Heusler alloys (0⩽⩽1), proposing new candidates with significantly enhanced nontrivial transport properties.
View Article and Find Full Text PDFJ Phys Chem Lett
August 2025
Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931, United States.
Inspired by the rich physics of honeycomb-kagome (HK) lattices and flat-band magnetism, we predict a stable two-dimensional (2D) penta-AgN monolayer through comprehensive tight-binding (TB) model analysis and first-principles calculations. This novel material integrates pentagonal AgN building blocks into an effective HK superstructure, exhibiting a unique planar hexagonal geometry with hypercoordinated Ag atoms. We demonstrate that penta-AgN is intrinsically a bipolar magnetic semiconductor (BMS) and, more notably, a magnetic real Chern insulator (MRCI) protected by symmetry, featuring spin-polarized flat bands near the Fermi level, intrinsic in-plane ferromagnetic ordering, and observable corner states.
View Article and Find Full Text PDFJ Phys Condens Matter
August 2025
Centre for Nanotechnology, IIT Roorkee, Roorkee, Uttarakhand 247667, India.
The Fermi surface topology of a triple non-hermitian (NH) Weyl-semimetal (WSM) driven by bi-circularly (BCL) polarized light is presented in this study. A NH WSM in particular has remarkable outlines. BCL light, however, modifies the symmetry features of NH triple Weyl and causes an unusual new kind of band swapping.
View Article and Find Full Text PDFSci Bull (Beijing)
August 2025
Fujian Key Laboratory of Quantum Information and Quantum Optics, College of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China; Hefei National Laboratory, Hefei 230088, China. Electronic address:
Non-Hermiticity can lead to the emergence of many intriguing phenomena that are absent in Hermitian systems, enabled by exceptional topological defects, among which Weyl exceptional rings (WER) are particularly interesting. The topology of a WER can be characterized by the quantized Berry phase and a nonzero Chern number, both encoded in the eigenvectors of the non-Hermitian Hamiltonian. So far, WERs have been realized with classical wave systems, whose eigenvectors can be well described by classical physics.
View Article and Find Full Text PDFNanomaterials (Basel)
May 2025
State Key Laboratory of Advanced Refractories, Wuhan University of Science and Technology, Wuhan 430081, China.
The low-symmetry Weyl semimetallic Td-phase WTe exhibits both a distinct out-of-plane damping torque (τDL) and exceptional charge-spin interconversion efficiency enabled by strong spin-orbit coupling, positioning it as a prime candidate for spin-orbit torque (SOT) applications in two-dimensional transition metal dichalcogenides. Herein, we report on thickness-dependent unconventional out-of-plane τDL in chemically vapor-deposited (CVD) polycrystalline Td-WTe ()/NiFe/MgO/Ti (Td-WTN-) heterostructures. Angle-resolved spin-torque ferromagnetic resonance measurements on the Td-WTN-12 structure showed significant spin Hall conductivities of = 4.
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