arXiv subjects

Zhejunyu Jin

Publications and source records attributed to Zhejunyu Jin.

15 recordsLinked to original sources

arXiv2026

Instability of two-dimensional nonrelativistic altermagnets

Altermagnets (AMs) are collinear compensated magnets that exhibit momentum-dependent spin splitting without requiring a net magnetization. Since local magnetic moments and exchange-driven order do not rely on relativistic effects, altermagnetism can be naturally formulated in a nonrelativistic spin-group framework. This raises a basic question: can two-dimensional altermagnetic order be stabilized by purely exchange interactions in the absence of spin-orbit-induced anisotropy? We address this question by applying Bogoliubov's inequality to a minimal $d$-wave altermagnetic spin model. We show that the anisotropic exchange pattern responsible for altermagnetism still contributes only a quadratic long-wavelength term to the Bogoliubov denominator. Consequently, short-ranged exchange interactions alone cannot stabilize long-range altermagnetic order in two dimensions when continuous spin-rotation symmetry is preserved. In contrast, the corresponding three-dimensional system has a finite small-momentum contribution and is not ruled out by the Mermin-Wagner argument.

cond-mat.mtrl-sci↗

arXiv2026

Rolling Two-Dimensional Collinear Magnets into Chiral Nanotubes with $p$-Wave Magnetism

$p$-wave magnets are noncollinear compensated magnetic systems that exhibit nonrelativistic antisymmetric spin splitting in momentum space. Their odd-parity spin symmetry enables unconventional spintronic functionalities, including highly efficient charge-to-spin conversion via the Edelstein effect. An outstanding question is whether such magnetic phases can emerge from simple and broadly accessible magnetic building blocks rather than from intrinsically noncollinear magnetic orders. Here, we show that rolling two-dimensional collinear magnets -- ferromagnets, antiferromagnets, and altermagnets -- into nanotubes generates a rich spin-symmetry landscape controlled by curvature, chirality, and magnetic order. Remarkably, chiral nanotubes hosting radial or tangential coplanar spin textures generically realize $p$-wave magnetism irrespective of the underlying collinear parent phase. The emergent odd-parity spin symmetry manifests itself in both electronic and magnonic spectra through antisymmetric $p$-wave spin splitting. Our results establish magnetic nanotubes as a versatile platform for engineering unconventional $p$-wave magnetism and predict a nonrelativistic Edelstein response that exceeds conventional spin-orbit-driven charge-to-spin conversion by more than an order of magnitude.

cond-mat.mes-hall↗

arXiv2026

Current-driven nonlinear skyrmion dynamics in altermagnets

The center of mass and helicity are two dynamic degrees of freedom of skyrmions. In this work, we study the current-driven skyrmion motion in frustrated altermagnets. Contrary to conventional wisdom, we find that the skyrmion helicity is not locked with the skyrmion Hall angle, but unidirectionally rotates with a global angular velocity proportional to the square of the current density. In addition, we find that the helicity rotation velocity is highly anisotropic, depending on the direction of current flows. We also observe helicity oscillation in the terahertz regimes, where the nonlinear mixing between the fast and slow modes generates a magnon frequency comb. Full atomistic spin dynamics simulations verify our theoretical predictions. Our results establish frustrated altermagnets as a promising platform for skyrmionics, THz technology, and frequency comb.

cond-mat.mtrl-sci↗

arXiv2026

Alignment-Dependent Gapless Chiral Split Magnons in Altermagnetic Domain Walls

Altermagnets, an emerging class of magnetic materials, exhibit exotic chiral split magnons that are of great interest for both fundamental physics and spintronic applications. However, detecting and manipulating these magnons is challenging due to their THz frequency response. Here, we report the discovery of gapless chiral split magnons confined within altermagnetic domain walls. Unlike in conventional ferromagnets or antiferromagnets, their spectrum is highly sensitive to the domain wall orientation relative to the crystal axis. These magnons inherit the chiral splitting of their bulk counterparts and are detectable in the microwave regime, offering a distinctive signature for identifying altermagnets. We further show that the interfacial Dzyaloshinskii-Moriya interaction drives hybridization of magnons with opposite chiralities, enabling unidirectional strong magnon-magnon coupling. Moreover, we demonstrate that spin-orbit torque can control the domain wall orientation, providing a practical means to manipulate these chiral magnons. Our findings open pathways for novel magnonic nanocircuitry based on altermagnetic domain walls.

cond-mat.mes-hall↗

arXiv2025

Topological Magnon Frequency Combs

Exploring the synergy between topological physics and nonlinear dynamics unveils profound insights into emergent states of matter. Inspired by recent experimental demonstrations of topological frequency combs in photonics, we theoretically introduce topological magnon frequency combs (MFCs) in a two-dimensional triangular skyrmion lattice. Computing the Chern numbers of magnon bands reveals robust chiral edge states. Strikingly, these topological MFCs originate from nonlinear four-magnon scattering among the chiral edge modes, activated by dual-frequency driving without an amplitude threshold. Comb spacings are readily tunable through excitation frequency detuning. Micromagnetic simulations validate our predictions with good concordance. This work paves the way for defect-immune magnonic devices exploiting MFCs and sparks investigations into topological-nonlinear phenomena in magnetic systems.

cond-mat.mes-hall↗

arXiv2025

Interaction-Driven Altermagnetic Magnon Chiral Splitting

Nonrelativistic magnon chiral splitting in altermagnets has garnered significant recent attention. In this work, we demonstrate that nonlinear three-wave mixing -- where magnons split or coalesce -- extends this phenomenon into unprecedented relativistic regimes. Employing a bilayer antiferromagnet with Dzyaloshinskii-Moriya interactions, we identify three distinct classes of chiral splitting, each dictated by specific symmetries, such as $C_4T$, $\sigma_v T$, or their combination. This reveals a novel bosonic mechanism for symmetry-protected chiral splitting, capitalizing on the unique ability of magnons to violate particle-number conservation, a feature absent in low-energy fermionic systems. Our findings pave the way for engineering altermagnetic splitting, with potential applications in advanced magnonic devices and deeper insights into magnon dynamics in complex magnetic systems.

cond-mat.mtrl-sci↗

arXiv2025

Frequency comb in twisted magnonic crystals

While twisted magnonic crystals (MCs) have recently gained attention for their intriguing linear phenomena, such as magnon flat bands, their nonlinear dynamics -- particularly the generation of magnonic frequency combs (MFCs) -- have remained largely unexplored. In this work, we demonstrate the creation of MFCs in twisted MCs using two-tone microwave excitation. We find that finite twist angles significantly enhance three-magnon interactions, driven by the non-collinear ground-state magnetic configuration induced by interlayer dipole-dipole interactions. The number of comb teeth exhibits a plateau-like dependence on the twist angle, with the plateau's width and height saturating as the excitation frequency of the propagating magnon mode increases. This behavior reveals an optimal range of twist angles and frequencies for achieving high-quality MFCs with a large number of comb teeth. Our findings deepen the understanding of nonlinear interactions in twisted MCs and highlight their potential for advancing moir\'e-based materials in information processing and high-precision metrology.

cond-mat.mtrl-sci↗

arXiv2025

Magnon-Driven Phononic Frequency Comb in Linear Elastic Media

Phononic frequency combs (PFCs) typically require nonlinear elastic media, limiting their frequency range and stability. Here, we propose a transformative approach to generate PFCs in purely linear elastic media by harnessing the magnon nonlinearities, offering a new paradigm for frequency comb physics. By tuning the magnon-phonon coupling confined in a magnetic disk of a vortex state into the strong coupling regime, we demonstrate an efficient nonlinearity transfer from magnons to phonons. This mechanism is able to produce GHz-range PFCs with comb spacing set by the vortex core's gyration frequency. Full micromagnetic simulations verify our theoretical predictions, confirming robust comb formation at 3.5 GHz with 0.4 GHz spacing. This approach overcomes the sub-MHz constraints of conventional PFCs, enabling applications in high-precision metrology, nanoscale sensing, and quantum technologies. Our findings also deepen the understanding of the nonlinear dynamics in hybrid magnon-phonon systems and provide a versatile platform for exploring frequency combs in diverse physical systems.

cond-mat.mes-hall↗

arXiv2025

Strong coupling of chiral magnons in altermagnets

Altermagnets recently are identified as a new class of magnets that break the time-reversal symmetry without exhibiting net magnetization. The role of the dipole-dipole interaction (DDI) on their dynamical properties however is yet to be addressed. In this work, we show that the DDI can induce the strong coupling between exchange magnons with opposite chiralities in altermagnets, manifesting as a significant level repulsion in the magnon spectrum. Crucially, the predicted magnon-magnon coupling is highly anisotropic, and observable in practical experiments. These exotic features are absent in conventional antiferromagnets. Our findings open a new pathway for quantum magnonic information processing based on altermagnetism.

cond-mat.mtrl-sci↗

arXiv2024

Low-lying magnon frequency comb in skymion crystals

A stable, low-power and tunable magnon frequency comb (MFC) is crucial for magnon-based precision measurements, quantum information processing and chip integration. Original method for creating MFC utilizes the nonlinear interactions between propagating spin waves and localized oscillations of an isolated magnetic texture, e.g., skyrmion. It requires a driving frequency well above the ferromagnetic resonance (FMR) and the spectrum frequency of MFC will quickly approach to the detection limit of conventional microwave technique after only tens of comb teeth. In addition, the detection and manipulation of a single skyrmion is challenging in experiments due to its high degree of locality. These issues hinder the applications of MFC. In this work, we report the low-lying MFC with comb frequencies below the FMR in a skyrmion crystal (SkX). We show that the MFC originates from the three-wave mixing between the collective skyrmion gyration and breathing in the SkX. Our findings significantly improve the efficiency of the nonlinear frequency conversion from a single-frequency mircowave input, and establish a synergistic relationship between the SkX and MFC, which paves the way to coherent information processing and ultra-sensitive metrology based on MFC.

cond-mat.mtrl-sci↗

arXiv2024

Skyrmion Hall effect in altermagnets

It is widely believed that the skyrmion Hall effect is absent in antiferromagnets because of the vanishing topological charge. However, the Aharonov-Casher theory indicates the possibility of topological effects for neutral particles. In this work, we predict the skyrmion Hall effect in emerging altermagnets with zero net magnetization and zero skyrmion charge. We first show that the neutral skyrmion manifests as a magnetic quadrupole in altermagnets. We reveal a hidden gauge field from the magnetic quadrupole, which induces the skyrmion Hall effect when driven by spin transfer torque. Interestingly, we identify a sign change of the Hall angle when one swaps the anisotropic exchange couplings in altermagnets. Furthermore, we demonstrate that both the velocity and Hall angle of altermagnetic skyrmions sensitively depend on the current direction. Our findings real the critical role of magnetic quadrupole in driving the skyrmion Hall effect with vanishing charge, and pave the way to discovering new Hall effect of neutral quasiparticles beyond magnetic skyrmions.

cond-mat.mtrl-sci↗

arXiv2023

Terahertz magnon frequency comb

Magnon frequency comb (MFC), the spin-wave spectra composing of equidistant coherent peaks, is attracting much attention in magnonics. A terahertz (THz) MFC, combining the advantages of the THz and MFC technologies, is highly desired because it would significantly advance the MFC applications in ultrafast magnonic metrology, sensing, and communications. Here, we show that the THz MFC can be generated by nonlinear interactions between spin waves and skyrmions in antiferromagnets [Z. Jin \emph{et al}., \href{https://doi.org/10.48550/arXiv.2301.03211}{arXiv:2301.03211}]. It is found that the strength of the three-wave mixing between propagating magnons and breathing skyrmions follows a linear dependence on the driving frequency and the MFC signal can be observed over a broad driving frequency range. Our results extend the working frequency of MFC to the THz regime, which would have potential applications in ultrafast spintronic devices and promote the development of nonlinear magnonics in antiferromagnets.

cond-mat.mes-hall↗

arXiv2023

Cavity-Induced Strong Magnon-Magnon Coupling in Altermagnets

Long-distance strong coupling between short-wavelength magnons remains an outstanding challenge in quantum magnonics, an emerging interdiscipline between magnonics and quantum information science. Recently, altermagnets are identified as the third elementary class of magnets that break the time-reversal symmetry without magnetization and thus combine characteristics of conventional collinear ferromagnets and antiferromagnets. In this work, we show that cavity photons can mediate the long-distance strong coupling of exchange magnons with opposite chiralities in altermagnets, manifesting as an anticrossing of the magnon-polariton spectrum in the extremely dispersive regime. The predicted effective magnon-magnon coupling strongly depends on the magnon propagation direction, and is thus highly anisotropic. Our findings are intimately connected to the intrinsic nature of altermagnetic magnons, i.e., chirality-splitting-induced crossing of exchange magnons, which has no counterpart in conventional ferromagnets or antiferromagnets, and may open a new path way for magnon-based quantum information processing in altermagnets.

cond-mat.mtrl-sci↗

arXiv2023

Nonlinear Topological Magnon Spin Hall Effect

When a magnon passes through two-dimensional magnetic textures, it will experience a fictitious magnetic field originating from the $3\times 3$ skew-symmetric gauge fields. To date, only one of the three independent components of the gauge fields has been found to play a role in generating the fictitious magnetic field while the rest two are perfectly hidden. In this work, we show that they are concealed in the nonlinear magnon transport in magnetic textures. Without loss of generality, we theoretically study the nonlinear magnon-skyrmion interaction in antiferromagnets. By analyzing the scattering features of three-magnon processes between the circularly-polarized incident magnon and breathing skyrmion, we predict a giant Hall angle of both the confluence and splitting modes. Furthermore, we find that the Hall angle reverses its sign when one switches the handedness of the incident magnons. We dub it nonlinear topological magnon spin Hall effect. Our findings are deeply rooted in the bosonic nature of magnons that the particle number is not conserved, which has no counterpart in low-energy fermionic systems, and may open the door for probing gauge fields by nonlinear means.

cond-mat.mes-hall↗

arXiv2020

Enhanced Stability of Antiferromagnetic Skyrmion during Its Motion by Anisotropic Dzyaloshinskii Moriya Interaction

Searching for new methods to enhance the stability of antiferromagnetic (AFM) skyrmion during its motion is an important issue for AFM spintronic devices. Herein, the spin polarized current-induced dynamics of a distorted AFM skyrmion is numerically studied, based on the Landau Lifshitz Gilbert simulations of the model with an anisotropic Dzyaloshinskii Moriya (DM) interaction. It is demonstrated that the DM interaction anisotropy induces the skyrmion deformation, which suppresses the distortion during the motion and enhances the stability of the skyrmion. Moreover, the effect of the DM interaction anisotropy on the skyrmion velocity is investigated in detail, and the simulated results are further explained by Thiele theory. This work unveils a promising strategy to enhance the stability and the maximum velocity of AFM skyrmion, benefiting future spintronic applications.

physics.app-ph↗