arXiv subjects

H. Y. Yuan

Publications and source records attributed to H. Y. Yuan.

At least 19 recordsLinked to original sources

arXiv2026

Strong coupling between antiferromagnetic magnons and spoof surface plasmons

Hybrid magnonic system provides a versatile platform for coherent information exchange between spin excitations and other physical degrees of freedom. While strong coupling between magnons and spoof plasmons has been observed based on ferrimagnetic spheres and localized microwave resonators, it remains unexplored whether coherent magnon-plasmon coupling can be achieved in planar magnetic structures. Here we study the hybridization of antiferromagnetic (AFM) magnons and spoof surface plasmons in a planar heterostructure consisting of an AFM thin film, a dielectric spacer, and a structured metal surface. By analytically solving the coupled Maxwell and magnetization dynamics equation, we predict strong magnon-plasmon coupling in the terahertz regime, manifested by pronounced avoided crossings in the dispersion. The coupling originates from the spatial overlap between magnonic and plasmonic modes in the dielectric spacer, and can be efficiently tuned through geometric parameters of the system. The calculated cooperativity confirms that the hybrid system can operate in the strong coupling regime, enabling coherent information transfer between magnons and plasmons. Our results establish a planar platform for plasmon-magnon hybridization, which is more amenable to on-chip manipulation and integration.

cond-mat.mes-hall↗

arXiv2026

Giant mode splitting of azimuthal spin waves in radial vortices

Radial vortex is a topological spin texture stabilized by the interfacial Dzyaloshinskii-Moriya interaction (DMI) in ferromagnetic disks. Previous investigations have shown that the doublet splitting of azimuthal modes in traditional circular vortices arises from the coupling between azimuthal spin waves and vortex core (VC), an effect occurs only for azimuthal indices $m=\pm1$ and is absent for higher-order modes. Here, we present a giant mode splitting of azimuthal spin waves in radial vortices, even in the absence of the VC. This mode splitting arises from the DMI, which can be an order of magnitude larger than that induced by the VC. Moreover, the DMI-induced frequency splitting increases with both the DMI constant and mode index, reaching tens of GHz for higher-order azimuthal modes. Our results reveal a robust mechanism for mode splitting in chiral magnetic textures and deepen the fundamental understanding of the DMI effect on the spin-wave dynamics in confined magnets.

cond-mat.mes-hall↗

arXiv2026

Paradoxes Are Not Contradictions: Re-examining the Third Mathematical Crisis

Russell's paradox was proposed in the early 20th century to address loopholes in set theory, which directly triggered the third mathematical crisis. This paper proposes and elaborates a perspective distinct from previous studies: paradoxes do not give rise to contradictions; instead, they constitute a Möbius strip-style self-consistent logical structure via self-reference and negation under the logical rules within a system. Gödel's incompleteness theorems indicate that such structures universally exist in formal logical systems. Turing proved the undecidability of the halting problem by first assuming the existence of a halting program and subsequently refuting this assumption through paradox construction, and this paper demonstrates flaws inherent to such proof strategy. Cases of paradoxes within three-valued logical systems are further discussed in this work, where the undecidability of paradoxes is rigorously proven. Finally, inspirations drawn from paradoxes for the real world are explored: two opposing factors can be integrated through the joint mechanism of self-reference and negation. A representative example is the wave-particle duality of light, whose essence may be interpreted as a paradox of waves and particles.

math.GM↗

arXiv2026

Harnessing Plasmonic Heating For Switching In Antiferromagnets

Heat waste is a bottleneck in the development of green information technologies and much effort has been devoted to suppress the heating effect in both electronic and spintronic devices. Here we take an alternative approach and show that controllable heating at the nanoscale can actually benefit information processing. In particular, we study a hybrid nanostructure consisting of a metallic square frame and an antiferromagnetic (AFM) thin film and show that the plasmonic heating can reversibly switch two perpendicularly-oriented AFM domains without the assistance of magnetic fields and electric currents. The required switching energy is at the order 1 nJ, three to six orders of magnitude lower than the current-driven AFM switching. The physical mechanism arises from the thermal-induced strain fields inside the frame, which couple to and manipulate the magnetic orientation via magnetoelastic effect. The strain field direction can be well controlled by selectively exciting the longitudinal and transverse plasmon modes by varying the polarization of the waves, which readily allows for a reversible switching of the AFM vector. Our findings provide tremendous opportunities for optically manipulating the magnetism with ultralow energy consumption and may further promote the interdisciplinary study of photonics, acoustics and spintronics.

cond-mat.mes-hall↗

arXiv2026

Reversible Steady Domain-Wall Motion Driven by a Direct Current

Understanding and manipulating nanoscale domain wall (DW) dynamics is a central topic in magnetism and spintronics for its promising applications in logic and memory devices. In most magnetic systems, inertia affects only transient DW dynamics, while the long-time DW motion is uniquely determined by the magnitude and direction of the applied current. Here we show that this paradigm breaks down in ferrimagnets near the angular momentum compensation point. We demonstrate that a DW can propagate steadily either forward or backward even under a direct current, with the direction controlled solely by the current strength. This anomalous phenomenon originates from the inertial dynamics of an internal DW collective coordinate, which behaves as a massive object evolving in a current-dependent double-well potential. Depending on the driving current, the system relaxes into distinct stable states associated with opposite directions of motion. Our findings reveal an unexpected role of inertia in nonlinear spin dynamics, and enable low-energy spintronic functionalities including sensitive magnetic-field detection and reconfigurable one-port devices.

cond-mat.mes-hall↗

arXiv2025

Macroscopic entanglement between localized domain walls inside a cavity

We present a scheme for generating stable and tunable entanglement between two localized Bloch domain walls in nanomagnetic strips kept inside a chiral optical cavity. The entanglement is mediated by the effective optomechanical interaction between the cavity photons and the two macroscopic, collective modes of the pinned domain walls. By controlling the pinning potential and optical driving frequency, the robust, steady-state entanglement between the two macroscopic domain walls can survive beyond the typical milli-Kelvin temperature range.

quant-ph↗

arXiv2025

Using surface plasmons to detect spin inertia

Recent experiments demonstrate that spin dynamics may acquire an inertial effect in a few metallic magnets, deviating from the traditional inertia-free dynamics. It remains an open question to ascertain the physical mechanisms and universality of the spin inertia across diverse magnetic systems. Here, we show that spin inertia generates nutation spin waves in the terahertz regime, which can hybridize with the surface plasmons in two-dimensional (2D) conducting materials such as graphene. By exciting hybrid spin wave-plasmon modes and analyzing the reflection spectrum of a 2D material$|$magnet heterostructure, we propose a method to quantitatively determine the strength of spin inertia in magnetic layers. Our approach is universally applicable to all types of magnetic insulators and could advance the future exploration of the magnitude and physical mechanism of spin inertia.

cond-mat.mes-hall↗

arXiv2025

Plasmon-Driven Giant Amplification of Ultrashort Spin Current

A key challenge in spintronics is to efficiently generate and manipulate spin current for information processing. Here we study ultrashort spin transport and associated terahertz (THz) emission in a hybrid structure comprising gold nanoparticles, a ferromagnet (FM) and a normal metal (NM) and show that plasmon excitation in the nanoparticles strongly enhances the electron-magnon scattering rate through heating effects, thereby amplifying the spin current generation at the FM$|$NM interface. This effect is even more pronounced when the FM is an insulator with a thickness much smaller than the nanoparticle size. In this case, the gold nanoparticle and NM substrate form a nanocavity with the FM as a dielectric layer, trapping plasmons inside the gap. The resulting spin current can be amplified by two orders of magnitude as compared to the case without plasmon excitations. Our findings provide a novel route to design efficient spintronic THz devices and further open the door to the interdisciplinary field of spintronics and nanophotonics.

cond-mat.mes-hall↗

arXiv2024

Quantum entanglement and Einstein-Podolsky-Rosen steering in magnon frequency comb

Significant progress has been made for the emerging concept of magnon frequency comb (MFC) but mainly in the classical region. The quantum property of the comb structure is yet to be explored. Here we theoretically investigate the quantum fluctuations of frequency combs and demonstrate the continuous-variable quantum entanglement and Einstein-Podolsky-Rosen (EPR) steering between different teeth of MFC. Without loss of generality, we address this issue in a hybrid magnon-skyrmion system. We observe a strong two-mode squeezed entanglement and asymmetric steering between the sum- and difference-frequency magnon teeth mediated by the skyrmion that acts as an effective reservoir to cool the Bogoliubov mode delocalized over the first-order magnon pair in MFC. Our findings show the prominent quantum nature of MFC, which has the potential to be utilized in ultrafast quantum metrology and multi-task quantum information processing.

quant-ph↗

arXiv2024

Strong and tunable coupling between antiferromagnetic magnons and surface plasmons

Surface plasmons are the collective electron excitations in metallic systems and the associated electromagnetic wave usually has the transverse magnetic (TM) polarization. On the other hand, spin waves are the spin excitations perpendicular to the equilibrium magnetization and are usually circularly polarized in a ferromagnet. The direct coupling of these two modes is difficult due to the difficulty of matching electromagnetic boundary conditions at the interface of magnetic and non-magnetic materials. Here, we overcome this challenge by utilizing the linearly polarized spin waves in antiferromagnets (AFM) and show that a strong coupling between AFM magnons and surface plasmons can be realized in a hybrid 2D material/AFM structure, featuring a clear anticrossing spectrum at resonance. The coupling strength, characterized by the gap of anticrossing at resonance, can be tuned by electric gating on 2D materials and be probed by measuring the two reflection minima in the reflection spectrum. Further, as a potential application, we show that plasmonic modes can assist the coupling of two well-separated AFMs over several micrometers, featuring symmetric and antisymmetric hybrid modes. Our results may open a new platform to study antiferromagnetic spintronics and its interplay with plasmonic photonics.

cond-mat.mes-hall↗

arXiv2024

Breaking surface plasmon excitation constraint via surface spin waves

Surface plasmons in two-dimensional (2D) electron systems have attracted great attention for their promising light-matter applications. However, the excitation of a surface plasmon, in particular, transverse-electric (TE) surface plasmon, remains an outstanding challenge due to the difficulty to conserve energy and momentum simultaneously in the normal 2D materials. Here we show that the TE surface plasmons ranging from gigahertz to terahertz regime can be effectively excited and manipulated in a hybrid dielectric, 2D material and magnet structure. The essential physics is that the surface spin wave supplements an additional freedom of surface plasmon excitation and thus greatly enhances the electric field in the 2D medium. Based on widely-used magnetic materials like yttrium iron garnet (YIG) and manganese difluoride ($\mathrm{MnF}_2$), we further show that the plasmon excitation manifests itself as a measurable dip in the reflection spectrum of the hybrid system while the dip position and the dip depth can be well controlled by an electric gating on the 2D layer and an external magnetic field. Our findings should bridge the fields of low-dimensional physics, plasmonics and spintronics and open a novel route to integrate plasmonic and spintronic devices.

cond-mat.mes-hall↗

arXiv2024

Single-mode spin-wave laser driven by spin-orbit torque

A central goal in spintronics and magnonics is the use of spin waves rather than electrons for efficient information processing. The key to integrate such spintronic circuits with electronic circuits is the ability to inject, control and detect coherent spin waves with charge currents. Here, we propose a tunable setup consisting of a synthetic antiferromagnet in an inhomogeneous magnetic field in which one of the magnetic layers is thin and biased by spin-orbit torque. We show that for appriopriate conditions single-mode coherent spin waves are emitted in this set-up. The set-up implements coupling of continuum spin waves with a finite region of negative energy spin waves, such that specific frequencies become self-amplified and thus start lasing. We show there exist a large region in parameter space for which the coherent spin wave laser is stabilized by non-linearities and spin-orbit torques. Our findings may lead to new ways of injecting coherent spin waves with direct currents.

cond-mat.mes-hall↗

arXiv2024

Bath-induced spin inertia

Spin dynamics is usually described as massless or, more precisely, as free of inertia. Recent experiments, however, found direct evidence for inertial spin dynamics. In turn, it is necessary to rethink the basics of spin dynamics. Focusing on a macrospin in an environment (bath), we show that the spin-to-bath coupling gives rise to spin inertia. This bath-induced spin inertia appears universally from all the high-frequency bath modes. We expect our results to provide new insights into recent experiments on spin inertia. Moreover, they indicate that any channel for spin dissipation should also be accompanied by a term accounting for bath-induced spin inertia. As an illustrative example, we consider phonon-bath-induced spin inertia in a YIG/GGG stack.

cond-mat.mes-hall↗

arXiv2023

Tutorial: Nonlinear magnonics

Nonlinear magnonics studies the nonlinear interaction between magnons and other physical platforms (phonon, photon, qubit, spin texture) to generate novel magnon states for information processing. In this tutorial, we first introduce the nonlinear interactions of magnons in pure magnetic systems and hybrid magnon-phonon and magnon-photon systems. Then we show how these nonlinear interactions can generate exotic magnonic phenomena. In the classical regime, we will cover the parametric excitation of magnons, bistability and multistability, and the magnonic frequency comb. In the quantum regime, we will discuss the single magnon state, Schrödinger cat state and the entanglement and quantum steering among magnons, photons and phonons. The applications of the hybrid magnonics systems in quantum transducer and sensing will also be presented. Finally, we outlook the future development direction of nonlinear magnonics.

cond-mat.mes-hall↗

arXiv2023

Magnon bundle in a strongly dissipative magnet

Hybrid quantum systems based on magnetic platforms have witnessed the birth and fast development of quantum spintronics. Until now, most of the studies rely on magnetic excitations in low-damping magnetic insulators, particularly yttrium iron garnet, while a large class of magnetic systems is ruled out in this interdisciplinary field. Here we propose the generation of a magnon bundle in a hybrid magnet-qubit system, where two or more magnons are emitted simultaneously. By tuning the driving frequency of qubit to match the detuning between magnon and qubit mode, one can effectively generate a magnon bundle via super-Rabi oscillations. In contrast with general wisdom, magnetic dissipation plays an enabling role in generating the magnon bundle, where the relaxation time of magnons determines the typical time delay between two successive magnons. The maximal damping that allows an antibunched magnon bundle can reach the order of 0.1, which may break the monopoly of low-dissipation magnetic insulators in quantum spintronics and enables a large class of magnetic materials for quantum manipulation. Further, our finding may provide a scalable and generic platform to study multi-magnon physics and benefit the design of magnonic networks for quantum information processing.

cond-mat.mes-hall↗

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↗

arXiv2022

Antimagnonics

Magnons are the quanta of collective spin excitations in magnetically-ordered systems and manipulation of magnons for computing and information processing has witnessed the development of ``magnonics". A magnon corresponds to an excitation of the magnetic system from its ground state and the creation of a magnon thus increases the total energy of the system. In this perspective, we introduce the antiparticle of a magnon, dubbed the antimagnon, as an excitation that lowers the magnetic energy. We investigate the stability and thermal occupation of antimagnons and verify our theory by micromagnetic simulations. Furthermore, we show how the concept of antimagnons yields a unified picture to understand the magnonic analog of the Klein effect, magnonic black-hole horizons, and magnonic black-hole lasing. Our work may stimulate fundamental interest in antimagnons, as well as their applications to spintronic devices.

cond-mat.mes-hall↗

arXiv2022

Unidirectional magnetic coupling

We show that interlayer Dzyaloshinskii-Moriya interaction in combination with non-local Gilbert damping gives rise to unidirectional magnetic coupling. That is, the coupling between two magnetic layers -- say the left and right layer -- is such that dynamics of the left layer leads to dynamics of the right layer, but not vice versa. We discuss the implications of this result for the magnetic susceptibility of a magnetic bilayer, electrically-actuated spin-current transmission, and unidirectional spin-wave packet generation and propagation. Our results may enable a route towards spin-current and spin-wave diodes and further pave the way to design spintronic devices via reservoir engineering.

cond-mat.mes-hall↗