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We disclose the existence of a type of optical skyrmion, Gauss-Stokes (GS) skyrmions, that is naturally present in an optical vortex around its phase singularity. Contrary to previous research with optical skyrmions, we neither shape vector beams nor superpose different spatial modes and polarizations. In GS skyrmions, the phase singularity in the transversal field of a single monochromatic beam of uniform polarization (a scalar beam) is concealed by the axial field dictated by Gauss's divergence law, giving rise to a polarization singularity of undefined polarization plane. This singularity is enclosed by a rich skyrmionic polarization texture fulfilling a topological map and covering all the states of transverse-axial polarization. In our experiment, we facilitate the observation of a GS skyrmion with the predicted features using focused fields with an enhanced axial component.
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http://dx.doi.org/10.1103/ndy2-wxwx | DOI Listing |
J Phys Condens Matter
August 2025
Faculty of Energy Science, Kim Il Sung University, Ryongnam-Dong, Taesong District, Pyongyang, Ryongnam-Dong, Korea (the Democratic People's Republic of).
We use the truncated-unity functional renormalization group (TUFRG) to study many-body instabilities of correlated electrons in graphene doped near the van Hove singularity (VHS). The system is described by an extended Hubbard model including several Coulomb repulsions between neighboring sites. With the repulsion parameters, which turn out to be suitable for low-energy consideration of graphene, we find a spin-bond-order phase in the vicinity of the VHS.
View Article and Find Full Text PDFSci Rep
August 2025
Institute of Quantum Information Technology, Yonsei University, Seoul, 03722, Korea.
In this study, we investigate various geometric aspects of a photonic hexagonal lattice made of triple-leg stripline resonators (TSRs) in a circuit QED system. The inherent two-fold degenerate spatial modes of the TSR act as two distinct orbitals in our 2D lattice system. Remarkably the energy spectra of the system exhibits the dispersive quadratic band-touching to the top and bottom flat bands.
View Article and Find Full Text PDFJ Geom Anal
August 2025
TIFR Centre for Applicable Mathematics, PO Box 6503, GKVK PO, Sharada Nagar, Chikkabommasandra, Yelahanka New Town, 560065 Bangalore, Karnataka India.
In this article, we study the microlocal properties of the geodesic ray transform of symmetric -tensor fields on 2-dimensional Riemannian manifolds with boundary allowing the possibility of conjugate points. As is known from an earlier work on the geodesic ray transform of functions in the presence of conjugate points, the normal operator can be decomposed into a sum of a pseudodifferential operator ( DO) and a finite number of Fourier integral operators (FIOs) under the assumption of no singular conjugate pairs along geodesics, which always holds in 2-dimensions. In this work, we use the method of stationary phase to explicitly compute the principal symbol of the DO and each of the FIO components of the normal operator acting on symmetric -tensor fields.
View Article and Find Full Text PDFCirc Arrhythm Electrophysiol
August 2025
Department of Biomedical Engineering (E.R., I.R.E.), Northwestern University, Chicago, IL.
Background: Atrial fibrillation (AF) is a progressive disease involving both structural and functional remodeling. Although over the past decade, digital twin-guided therapy has been proposed and applied, accounting for cardiomyocyte functional remodeling remains challenging. We aimed to investigate the contribution of functional remodeling at the cellular level to AF pathogenesis in patients with fibrotic remodeling and to develop novel techniques to predict the location of reentrant drivers.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
IMDEA Materials Institute, Calle Eric Kandel, 2, 289006, Getafe, Madrid, Spain.
Non-Hermitian systems have recently shown new possibilities to manipulate wave scattering by exploiting loss, yet coherent perfect absorption at an exceptional point (CPA EP) remains elusive in acoustics. Here, we demonstrate it based on a two-channel waveguide with compact lossy resonators. We realize imbalanced losses crucial for CPA EP by using active components to independently modulate the non-Hermiticity.
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