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We numerically model a two-dimensional active nematic confined by a periodic array of fixed obstacles. Even in the passive nematic, the appearance of topological defects is unavoidable due to planar anchoring by the obstacle surfaces. We show that a vortex lattice state emerges as activity is increased, and that this lattice may be tuned from "ferromagnetic" to "antiferromagnetic" by varying the gap size between obstacles. We map the rich variety of states exhibited by the system as a function of distance between obstacles and activity, including a pinned defect state, motile defects, the vortex lattice, and active turbulence. We demonstrate that the flows in the active turbulent phase can be tuned by the presence of obstacles, and explore the effects of a frustrated lattice geometry on the vortex lattice phase.
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http://dx.doi.org/10.1103/PhysRevLett.132.018301 | DOI Listing |
J Phys Condens Matter
September 2025
Physics and Astronomy, UVic, 3800 Finnerty Road, Victoria, British Columbia, V8P 5C2, CANADA.
We report measurements of the normal-state and superconducting properties of thin-film NbTiN usingLi-detected nuclear magnetic resonance (-NMR). In these experiments, radioactiveLiprobes were implanted 21 nm below the surface of a NbTiN(91 nm) film in NbTiN/(91 nm)/AlN(4 nm)/Nb and its NMR response recorded (viaLi's-emissions) between 4.6 K and and 270 K in a 4.
View Article and Find Full Text PDFOrbital angular momentum (OAM) beams have brought the nonlinear light-matter interaction to a novel, to our knowledge, regime. In this work, we investigate the generation of high-order harmonics in atomic gases when the extreme nonlinear optical process is driven by the coaxial superposition of linearly polarized Laguerre-Gaussian (LG) modes. Specifically, we discuss the cases when the waist sizes of the two superposed LG modes are different (double-ring vortex beam) or the same (optical ring lattice).
View Article and Find Full Text PDFACS Nano
September 2025
Department of Physics and Astronomy, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Superconducting vortices can reveal electron pairing details and nucleate topologically protected states. Yet, vortices of bulk spin-triplet superconductors have never been visualized at the atomic scale. Recently, UTe has emerged as a prime spin-triplet superconductor, but its superconducting order parameter is elusive, and whether time-reversal symmetry (TRS) is broken remains unsettled.
View Article and Find Full Text PDFAdv Mater
August 2025
Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Large lossless currents in high-temperature superconductors (HTS) critically rely on dense defects with suitable size and dimensionality to pin vortices, with dislocations being particularly effective due to their 1D geometry to interact extensively with vortex lines. However, in non-metallic compounds such as HTS with rigid lattices, conventional deformation methods typically lead to catastrophic fracture rather than dislocation-mediated plasticity, making it a persistent challenge to introduce dislocations at high density. Here, an asymmetric stress field strategy is proposed using extrusion to directly nucleate a high density of dislocations in HTS by activating shear-driven lattice slip and twisting under superimposed hydrostatic compression.
View Article and Find Full Text PDFNatl Sci Rev
August 2025
State Key Laboratory of Quantum Functional Materials, School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
The recently discovered heavy-fermion superconductor, UTe, is an excellent candidate for spin-triplet superconductors in which electrons form spin-triplet Cooper pairs with spin = 1 and odd parity. Unconventional superconductivity often hosts unconventional vortices. Yet, the vortex core and lattice in UTe have not been directly visualized and characterized.
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