arXiv subjects

Katsuya Inoue

Publications and source records attributed to Katsuya Inoue.

10 recordsLinked to original sources

arXiv2026

Can non-orthogonal bases form stable skyrmionic beams?

Skyrmions, topologically stable spin textures, have recently garnered significant attention in optics promising robust high-density information transition and nontrivial light-matter interaction. It was believed that the optical skyrmionic beams should be constructed by superposition of two orthogonal spatial modes with orthogonal polarizations to obtain topologically stable propagation. Here, we surprisingly find that propagation-stable skyrmionic beams can still be formed by superpositions of neither orthogonal spatial modes nor orthogonal polarizations. We theoretically present the mechanism to control the stable skyrmionics beams through the hybrid superposition of modes from the Hermite-Gaussian and Laguerre-Gaussian families and experimentally control the longitudinal on-demand dynamics of the skyrmions. This work redefines the topological stability of optical skyrmions, breaks limits and reduces the requirement for manipulating topologically structured light for practical multidimensional implementation of topologically robust information technologies.

physics.optics↗

arXiv2025

Storage and retrieval of optical skyrmions with topological characteristics

Optical skyrmions are topological structures of light whose defining property, the skyrmion number, is robust against perturbations. This makes them attractive for applications in quantum information storage, where resilience to decoherence is paramount. However, their preservation during coherent storage remains unexplored. We report the first experimental demonstration of storing and retrieving optical skyrmions in a cold $^{87}$Rb vapor using a dual-path electromagnetically induced transparency memory. Crucially, we show that the skyrmion number remains invariant for storage times up to several microseconds, even when subjected to imbalanced loss between the two paths and substantial perturbations in control beam power. Our work demonstrates the survival of a non-trivial topological invariant in a quantum memory, marking a significant step towards topologically protected photonic technologies.

quant-ph↗

arXiv2025

Chiral Analogues of Knit Stitches Designed Using Chiral Topology

Fabrics are flexible thin structures made of entangled yarn or fibers, yet the topological bases of their mechanics remain poorly understood. For weft knitted fabrics, we describe how the entanglement of adjacent stitches contributes to the flexibility of the fabric. Interpreting heterogeneous stitch pairs as domain boundaries reveals that the step between pairs of neighboring stitches is responsible for direction-specific flexibility. In typical knitted fabrics, anisotropic flexibility can be attributed to latticed domain boundaries. The intersections between domain boundaries result in point defects that induce frustration that resembles the impossible Penrose stairs. We identify these by a chiral characteristic, defined summing the ascending or descending steps in a cycle surrounding the defect. Remarkably, seed fabric, a knit with high flexibility in both course and wale directions, is characterized as a racemic crystal of these chiral point defects.

cond-mat.soft↗

arXiv2024

HBT signature for clustered substructures probing primordial inhomogeneity in hot and dense QCD matter

We propose a novel approach to probe primordial inhomogeneity in hot and dense matter which could be realized in non-central heavy-ion collisions. Although the Hanbury Brown and Twiss (HBT) interferometry is commonly used to infer the system size, the cluster size should be detected if substructures emerge in space. We demonstrate that a signal peak in the HBT two-particle correlation stands at the relative momentum corresponding to the spatial scale of pseudo one-dimensional modulation. We assess detectability using the data prepared by an event generator (AMPT model) with clustering implemented in the particle distribution.

hep-ph↗

arXiv2019

Skyrmion instabilities and distorted spiral states in a frustrated chiral magnet

Magnetic skyrmions are particle-like topological excitations that recently generated much interest as candidates for future spintronic devices based on skyrmion small size, enhanced topological stability, and/or mutual interaction. Here we examine the properties of isolated skyrmions in a frustrated chiral magnet with competing Dzyaloshinskii-Moriya and frustrated exchange interactions. We show that the skyrmion size drastically decreases even for small values of competing stabilization mechanisms. Skyrmion mutual interaction remains attracting as is inherent for frustrated skyrmions, but the value of the Dzyaloshinskii constant regulates the number of minima in the interaction potentials. Moreover, the constructed phase diagrams for a chiral helimagnet contain a distorted spiral state that can be considered as a buffer between the helicoidal and conical one-dimensional modulations. The formulated concepts may further enhance the functionalities of spintronic devices. In particular, the controlled instability of skyrmions with respect to the conical state allows to obtain bimeron-like structures. Moreover, our results provide physical insight into the chiral states in the magnetic systems, e.g., in MnSi$_{1-x}$Ge$_x$.

cond-mat.mes-hall↗

arXiv2018

Current-induced shuttlecock-like movement of non-axisymmetric chiral skyrmions

Current-induced motion of non-axisymmetric skyrmions within angular phases of polar helimagnetis with the easy plane anisotropy is studied by micromagnetic simulations.Such non-axisymmetric skyrmions consist of a circular core and a crescent-shaped domain-wall region formed with respect to the tilted surrounding state. A current-driven motion of non-axisymmetric skyrmions exhibits two distinct time regimes: initially the skyrmions rotate towards the current flow direction and subsequently move along the current with the skyrmionic crescent first. According to the Thiele equation, the asymmetric distribution of the topological charge and the dissipative force tensor play an important role for giving the different velocities for the circular and the crescent-shaped constituent parts of the skyrmion what underlies such a shuttlecock-like movement. Moreover, the current-velocity relation depends on the tilt angle of the surrounding angular phase what makes in particular the transverse velocity of skyrmions sensitive to their field-driven configurational transformation.

cond-mat.mtrl-sci↗

arXiv2018

Toggle-switch-like crossover between two types of isolated skyrmions within the conical phase of cubic helimagnets

We investigate the field-induced crossover between two types of isolated skyrmions that exist within the conical phase of cubic helimagnets and orient themselves either along or perpendicular to the field. Such a crossover takes place for the same value of the field, at which the closely packed skyrmion lattice was predicted to stabilize in the A-phase region. The clusters and a skyrmion lattice comprised by the skyrmions perpendicular to the field, however, are unfavorable and lose their stability as compared with the skyrmions parallel to the field. We also followed transformation of perpendicular skyrmions into pairs of merons that rupture the helical state. An attractive interactions between different types of isolated skyrmions make it feasible to construct complex cluster states with the cubic arrangement of skyrmions.

cond-mat.mes-hall↗

arXiv2017

Chiral Soliton Lattice Formation in Monoaxial Helimagnet Yb(Ni$_{1-x}$Cu$_x$)$_3$Al$_9$

Helical magnetic structures and its responses to external magnetic fields in Yb(Ni$_x$Cu$_{1-x}$)$_3$Al$_9$, with a chiral crystal structure of the space group $R32$, have been investigated by resonant X-ray diffraction. It is shown that the crystal chirality is reflected to the helicity of the magnetic structure by a one to one relationship, indicating that there exists an antisymmetric exchange interaction mediated via the conduction electrons. When a magnetic field is applied perpendicular to the helical axis ($c$ axis), the second harmonic peak of $(0, 0, 2q)$ develops with increasing the field. The third harmonic peak of $(0, 0, 3q)$ has also been observed for the $x$=0.06 sample. This result provides a strong evidence for the formation of a chiral magnetic soliton lattice state, a periodic array of the chiral twist of spins, which has been suggested by the characteristic magnetization curve. The helical ordering of magnetic octupole moments, accompanying with the magnetic dipole order, has also been detected.

cond-mat.str-el↗

arXiv2016

Incommensurate--commensurate transitions in the mono-axial chiral helimagnet driven by the magnetic field

The zero temperature phase diagram of the mono-axial chiral helimagnet in the magnetic field plane formed by the components parallel and perpendicular to the helical axis is thoroughly analyzed. The nature of the transition to the commensurate state depends on the angle between the field and the helical axis. For field directions close to the directions parallel or perpendicular to the helical axis the transition is continuous, while for intermediate angles the transition is discontinuous and the incommensurate and commensurate states coexist on the transition line. The continuous and discontinuous transition lines are separated by two tricritical points with specific singular behaviour. The location of the continuous and discontinuous lines and of the tricritical points depend strongly on the easy-plane anisotropy, the effect of which is analyzed. For large anisotropy the conical approximation locates the transition line very accurately, although it does not predict the continuous transitions nor the tricitical behaviour. It is shown that for large anisotropy, as in CrNb3S6, the form of the transition line is universal, that is, independent of the sample, and obeys a simple equation. The position of the tricritical points, which is not universal, is theoretically estimated for a sample of CrNb3S6

cond-mat.str-el↗

arXiv2007

Magnetic Field versus Temperature Phase Diagram of the Spin-1/2 Alternating Chain Compound F5PNN

We have measured the specific heat of the S = 1/2 alternating Heisenberg antiferromagnetic chain compound pentafluorophenyl nitronyl nitroxide in magnetic fields using a single crystal and powder. A sharp peak due to field-induced magnetic ordering (FIMO) is observed in both samples. The H-T phase boundary of the FIMO of the single crystal is symmetric with respect to the central field of the gapless field region HC1 < H < HC2, whereas it is distorted for the powder whose ordering temperatures are lower. An analysis employing calculations based on the finite temperature density matrix renormalization group indicates the possibility of novel incommensurate ordering due to frustration in the powder around the central field.

cond-mat.str-el↗