Bimerons and Antibimerons in Magnetic Textures

• Bimerons and antibimerons are topologically nontrivial magnetic textures formed by bound meron and antimeron pairs in easy-plane systems.
• Their stabilization relies on the interplay of exchange, anisotropy, and Dzyaloshinskii–Moriya interaction, enabling controlled formation and manipulation.
• Current-driven dynamics and nonlinear interactions underpin their potential in advanced spintronic devices, racetrack memory, and neuromorphic computing.

Bimerons and antibimerons are topologically nontrivial, particle-like magnetic textures whose emergence, stability, and dynamics are central to the rapidly developing field of topological solitons in condensed matter systems and beyond. Distinguished from skyrmions by their internal structure and the easy-plane background in which they reside, bimerons and antibimerons consist of bound meron and antimeron (i.e., vortex–antivortex) pairs, resulting in localized textures with integer topological charge but fundamentally different symmetry properties from their out-of-plane, radially symmetric skyrmion relatives. The distinct symmetry, energetics, and response to fields, currents, disorder, and collective effects endow bimerons and antibimerons with unique advantages for next-generation spintronic, information processing, and even optical technologies.

1. Topological Structure and Classification

Bimerons are characterized by the pairing of two meronic building blocks—each with a winding number of ±1/2—into a composite object with integer topological charge $Q = \pm 1$. These textures are realized in easy-plane (in-plane magnetized) materials, contrasted with skyrmions that occur in easy-axis (out-of-plane magnetized) systems (Göbel et al., 2018, Goerzen et al., 11 Sep 2025). The defining topological charge is given by

$$Q(\mathbf{m}) = \frac{1}{4\pi} \int \mathbf{m} \cdot\left(\frac{\partial \mathbf{m}}{\partial x}\times \frac{\partial \mathbf{m}}{\partial y}\right)\, d^2 r,$$

with the meron–antimeron decomposition further resolved using the “meron identifier” (Goerzen et al., 11 Sep 2025). The bimeron’s core region carries a winding of the magnetization confined to the easy plane, while the magnetization tails out to a constant direction at infinity. Notably, these in-plane textures remain degenerate with their antibimeron counterparts (with opposite $Q$) at zero external field, protected by the U(1) symmetry of the easy-plane background.

Antibimerons are the topological mirror images (or antiparticles) of bimerons, possessing the opposite net topological charge and reversed vorticity or core polarization. Their degeneracy with bimerons at zero field is a haLLMark of easy-plane symmetry, and their mutual coexistence leads to rich nonlinear physics in two-dimensional magnets (Goerzen et al., 11 Sep 2025). In certain systems, asymmetric antibimerons (AABs), stabilized by crystal symmetry and Dzyaloshinskii–Moriya interaction (DMI) anisotropy, acquire additional structural asymmetry and distinct dynamical signatures (Vorobyev et al., 14 Oct 2024).

2. Formation, Stabilization, and Symmetry

The stabilization and physical realization of bimerons and antibimerons rely on the interplay between exchange, anisotropy, DMI, and external fields. In the archetype scenario, a stripe or helical phase in a chiral magnet is “broken” into finite-length segments—the endpoints of which are half-disk meron caps with $Q = 1/2$, which combine to form bimerons (Ezawa, 2010). The DMI favors chiral twisting and enforces compact domains, while the easy-plane anisotropy ensures that the spin configuration remains in-plane (Göbel et al., 2018, Zhang et al., 2020, Yang et al., 25 Jun 2024).

Bimerons emerge not only in bulk chiral magnets and synthetic antiferromagnets (SyAFMs) (Bhukta et al., 2023), but also in low-dimensional systems such as van der Waals magnets (CrSBr (Yang et al., 25 Jun 2024), Cr$_2$Ge$_2$Te$_6$ (Goerzen et al., 11 Sep 2025)) and thin strips with carefully tuned easy-axis anisotropy (Castro et al., 30 Nov 2024). Their nucleation can be induced by rapid thermal quenching (following a Kibble–Zurek mechanism) (Yang et al., 25 Jun 2024), by the introduction of nonmagnetic impurities that break stripes into finite domains (Silva et al., 2013), by field cycling through magnetic phase boundaries (as across a Morin transition in hematite (Jani et al., 2020)), or via direct imprinting from an adjacent ferromagnet in heterostructures (Thevenard et al., 5 Feb 2025).

Antibimerons, and more generally asymmetric antibimerons (AABs), are stabilized in systems with specific DMI anisotropies (e.g., $D_{2d}$ symmetry) (Vorobyev et al., 14 Oct 2024). In contrast to symmetric bimerons, AABs may host a dominant antivortex paired to a crescent-shaped vortex, enabled by anisotropic DMI terms of the form

$$\epsilon_\text{DM} = D \left[ \mathbf{e}_x \cdot (\mathbf{m}\times\partial_y\mathbf{m}) + \mathbf{e}_y \cdot(\mathbf{m}\times\partial_x\mathbf{m}) \right].$$

For bimerons (and their symmetric counterparts), degenerate particle–antiparticle pairs are possible under U(1) symmetry (Goerzen et al., 11 Sep 2025), as the energy contributions are invariant under global spin inversion.

3. Dynamics: Current-Driven Motion, Interactions, and Instabilities

The dynamics of bimerons and antibimerons are governed by the Landau–Lifshitz–Gilbert (LLG) equation, with additional spin–orbit torque (SOT) and spin–transfer torque (STT) terms accounting for the effect of spin-polarized currents (Göbel et al., 2018, Chen et al., 2 May 2025, Castro et al., 30 Nov 2024, Vorobyev et al., 14 Oct 2024). The gyrotropic and dissipative tensors that enter the Thiele equation for bimeron center-of-mass motion reflect their internal structure and symmetry, and yield the quantity known as the bimeron Hall effect—transverse motion akin to the skyrmion Hall effect but generally exhibiting distinct field, torque, and anisotropy dependencies (Chen et al., 2 May 2025, Castro et al., 30 Nov 2024).

Notable dynamical features include:

• Anisotropic motion: Bimerons possess direction-dependent response to applied current or torque orientation, with maximal Hall angle when driven perpendicular to magnetic domain walls and minimal Hall angle for parallel orientations (Chen et al., 2 May 2025). The Hall angle and mobility can be tuned by adjusting damping, nonadiabatic torque, and device geometry (e.g., confining edges).
• Current-induced proliferation and aggregation: Strong in-plane currents, particularly with large nonadiabatic torque and low damping, can induce significant proliferation of bimerons and their aggregation into honeycomb lattices, accompanied by lattice phase transitions after current cessation. The process is optimal in the presence of an appropriate out-of-plane field (Zhang et al., 10 Jul 2024).
• Edge and domain-wall effects: In finite nanostrips, bimerons are stabilized as edge states when the easy-axis anisotropy and current are orthogonal, leveraging repulsive interactions with boundaries to prevent annihilation and support robust, high-speed propagation along racetracks—even in curved geometries (Castro et al., 30 Nov 2024, Chen et al., 2 May 2025).
• Nonreciprocal and ratchet transport: Asymmetrical bimerons and AABs show nonreciprocal transport: the velocity magnitude and Hall angle can depend on current polarity and torque parameters, enabling current-controlled unidirectional motion and charge conversion through collision processes (Shen et al., 2022, Vorobyev et al., 14 Oct 2024).
• Collective and nonlinear effects: Chains of bimerons exhibit decreased collective mobility and correlated "worm-like" segmented motion in domain walls or patterned nanostripes, especially in the presence of periodic edge defects which stabilize multi-soliton configurations and induce oscillatory dynamics (Toledo-Marin et al., 2 Sep 2025). Pairwise bimeron interaction is governed by directionally anisotropic, power-law or exponential decay of the magnetization profile, fostering nonlinear soliton–soliton coupling (Goerzen et al., 11 Sep 2025).
• Antiferromagnetic dynamics: In antiferromagnets, bimerons exhibit ultrafast, inertial dynamics with no Hall drift due to the cancellation of the Magnus force, supporting high-speed, deflection-free motion advantageous for memory devices (Shen et al., 2019, Jani et al., 2020, Thevenard et al., 5 Feb 2025).

4. Lifetime, Stability, and Thermally Activated Phenomena

The lifetime of bimerons and antibimerons is governed by both energetic and entropic factors. In easy-plane magnets, the presence of gapless zero modes due to unbroken U(1) symmetry confers significant entropic stabilization (Goerzen et al., 11 Sep 2025). The lifetime $\tau$ follows an Arrhenius law with an effective attempt frequency $\Gamma_0$:

$$\tau = \Gamma_0^{-1} \exp\left( \frac{\Delta E}{k_B T} \right ),$$

where $\Delta E$ is the energy barrier from the minimum energy path obtained, for instance, via the geodesic nudged elastic band (GNEB) method. Entropic contributions to $\Gamma_0$ result in a lifetime that is only weakly temperature dependent despite potentially modest $\Delta E$ values—a crucial property for sustaining bimerons as robust information carriers at finite temperature.

Decay mechanisms involve anisotropic/elliptical shrinking of the soliton, contrasting with the isotropic collapse of skyrmions (Goerzen et al., 11 Sep 2025). Experimental signatures of thermal formation or annihilation, particularly in systems cooled across a phase transition (Kibble–Zurek mechanism), have been reported (Yang et al., 25 Jun 2024, Jani et al., 2020).

5. Experimental Realizations and Detection

Bimerons and antibimerons have been observed or predicted in a broad array of systems:

• Chiral magnets: In thin films of MnSi and FeCoSi, phase diagrams and transport signatures indicate the presence of bimerons, merons, and skyrmion-gas phases, supported by analytical models incorporating DMI and Zeeman energy (Ezawa, 2010, Silva et al., 2013).
• Synthetic antiferromagnets: Three-dimensional vector imaging (SEMPA, MFM, XMCD-PEEM) has resolved bimerons, merons, and antimerons in stack-engineered SyAFMs, with tunable global chirality and magnetic compensation (Bhukta et al., 2023).
• Van der Waals and room-temperature materials: Simulations and imaging in CrSBr, $\alpha$-Fe$_2$O$_3$, and Fe$_3$GeTe$_2$/Cr$_2$Ge$_2$Te$_6$ heterostructures highlight metastable bimerons/antibimerons, with degenerate populations and high room-temperature stability (Jani et al., 2020, Yang et al., 25 Jun 2024, Goerzen et al., 11 Sep 2025).
• Patterned nanostripes and domain walls: Stable propagation and collective states of bimerons (and by extension, antibimerons) have been achieved in magnetic stripes with engineered pinning arrays (Toledo-Marin et al., 2 Sep 2025).
• Optical systems: Bimeronic textures are generated in paraxial laser beams by superposing orthogonal Hermite–Gaussian or Bessel modes in the linear polarization basis, with experimental interferometry and Poincaré sphere projection confirming the topological equivalence to magnetic bimerons and the transformation properties to skyrmions or antibimerons (Allam et al., 18 Jan 2025).

Detection techniques include magnetic force microscopy (MFM), scanning electron microscopy with polarization analysis, and synchrotron-based photoemission electron microscopy with magnetic dichroism (XMCD-PEEM and XMLD-PEEM), which allow for both in-plane and out-of-plane spin component mapping.

6. Applications and Spintronic Functionalities

Bimerons and antibimerons hold promise for an array of spintronic and information technologies:

• Racetrack memory: By encoding binary ("±1") or ternary data in the presence/absence or sign of bimerons/antibimerons, and exploiting current-driven motion without skyrmion Hall deflection (especially in antiferromagnets or at angular momentum compensation points), reliable nonvolatile storage and logic architectures are accessible (Göbel et al., 2018, Chen et al., 2 May 2025, Castro et al., 30 Nov 2024, Shen et al., 2022).
• Reservoir and neuromorphic computing: The nonlinear, direction-dependent soliton interactions and the ease of proliferation and aggregation enable architectures for in-memory and neuromorphic computing, where dynamic, reconfigurable connectivity is advantageous (Toledo-Marin et al., 2 Sep 2025, Goerzen et al., 11 Sep 2025, Zhang et al., 10 Jul 2024).
• Nano-oscillators and nonlinear devices: Chaotic, Duffing-type dynamics generated by alternating currents or boundary-induced nonlinearities in bimeron systems can be harnessed for frequency-agile microwave devices or for chaos-based computation (Shen et al., 2019).
• Low-power and multi-lane devices: Coexisting bimerons and antibimerons with opposite drift directions enable dual-lane racetrack concepts, enhancing data robustness and throughput (Shen et al., 2020).
• Optical communications and quantum technologies: Bimeronic textures in structured beams provide new channels for robust, topologically protected data transmission and advanced quantum information encoding (Allam et al., 18 Jan 2025).
• Sensing and high-density memory: Entropic stabilization and compact out-of-plane core sizes allow for ultra-dense packing and minimized stray field interference, advancing three-dimensional memory concepts (Jani et al., 2020, Bhukta et al., 2023).

7. Outlook, Challenges, and Open Questions

Key open directions include:

• Systematic tuning of DMI, anisotropy, interlayer exchange, and compensation to optimize the stabilization and switching of bimeronic states, particularly under device operation conditions (Bhukta et al., 2023).
• Real-time imaging and experimental control of bimeron-antibimeron creation, annihilation, and collision events, and elucidation of the scaling of these processes with system size, disorder, and field/cooling parameters (Yang et al., 25 Jun 2024, Zhang et al., 10 Jul 2024).
• Extension to artificial and natural antiferromagnets where bimeron behavior can leverage ultrafast, relativistic dynamics for highly efficient spintronic devices (Jani et al., 2020, Shen et al., 2019, Thevenard et al., 5 Feb 2025).
• Engineering of domain walls, edge states, and patterned defect landscapes (e.g., periodic notches) for robust, synchronized, and collective control of bimeron trains and phase-coded logic elements (Castro et al., 30 Nov 2024, Toledo-Marin et al., 2 Sep 2025).
• Fundamental studies of entropic effects, lifetime enhancement, and collapse mechanisms—especially with regard to temperature stability and the role of gapless excitations (Goerzen et al., 11 Sep 2025).
• Exploration of optical analogs and photonic systems hosting bimerons and antibimerons, pushing the frontier of topological physics into new realms (Allam et al., 18 Jan 2025).

In conclusion, bimerons and antibimerons—through their topological robustness, unique symmetry properties, tunable dynamics, and emergent functionalities—form a cornerstone of contemporary research in topological solitons, and represent an attractive platform for realizing dense, efficient, and adaptive devices in both quantum and classical regimes across magnetism, photonics, and beyond.