arXiv subjects

Xiansi Wang

Publications and source records attributed to Xiansi Wang.

10 recordsLinked to original sources

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↗

arXiv2025

Domain wall skyrmion-based magnonic crystal

Magnonic waveguide based on domain wall (DW) is considered as a crucial breakthrough toward the realization of magnonic nanocircuits. However, the effective control of spin waves propagating in DWs remains to be explored. Here, we construct a magnonic crystal (MC) by using a chain of the domain wall skyrmions (DWSKs) to manipulate the spin-wave propagation in DWs. We show that the DWSK chain can be created by leveraging voltage-controlled Dzyaloshinskii-Moriya interaction. The DWSK-based MC opens magnonic bandgaps, which can be dynamically adjusted through magnetic fields modulating the DWSK size. Furthermore, the manipulation of spin waves by the DWSK-based MC maintains robust in curved DW, demonstrating its adaptability to complex device architectures. Our work provides an effective method to control the spin-wave propagation in DWs and paves the way for designing energy-efficient magnonic nanocircuits.

cond-mat.mes-hall↗

arXiv2024

Current-driven motion of magnetic domain-wall skyrmions

Domain-wall skyrmions (DWSKs) are topological spin textures confined within domain walls that have recently attracted significant attention due to their potential applications in racetrack memory technologies. In this study, we theoretically investigated the motion of DWSKs driven by spin-polarized currents in ferromagnetic strips. Our findings reveal that the motion of DWSKs is contingent upon the direction of the current. When the current is applied parallel to the domain wall, both spin-transfer torque (STT) and spin-orbit torque (SOT) can drive the DWSK along the domain wall. Conversely, for currents applied perpendicular to the domain wall, STT can induce DWSK motion by leveraging the skyrmion Hall effect as a driving force, whereas SOT-driven DWSKs halt their motion after sliding along the domain wall. Furthermore, we demonstrated the current-driven motion of DWSKs along curved domain walls and proposed a racetrack memory architecture utilizing DWSKs. These findings advance the understanding of DWSK dynamics and provide insights for the design of spintronic devices based on DWSKs.

cond-mat.mes-hall↗

arXiv2024

An energy-dependent broadening of Rashba-like spin splitting in Au2Sb surface alloy with periodic structural defect

Here, we report a novel AuSb 2D superstructure on Au(111) that shows agreements and discrepancies to the expected electronic features of the ideal 2D surface alloys with $\sqrt{3}\times\sqrt{3}$ periodicity. Using spin- and angle-resolved photoemission spectroscopy, we find a spin splitting of the alloy bands with antiparallel spin polarization, stemming from Rashba spin-orbit coupling. However, the observed Rashba bands are significantly broadened. Taking advantage of the good agreement between the experimental results and DFT calculations, we determine that the broadening of the Rashba band is due to the perturbations from the 3-pointed-star-shaped defects acting as nonresonant impurities in the Au2Sb superstructure. These periodic defects can shift the energy position of the Rashba band without breaking the in-plane rotational symmetry and mirror symmetry, which suggests that introducing periodic defects into a Rashba SOC system possesses a great potential in engineering the spin-dependent properties of spintronic devices.

cond-mat.mtrl-sci↗

arXiv2024

Chiral Quantum well Rashba splitting in Sb monolayer on Au(111)

We present a comprehensive investigation into the atomic and electronic structures of a single-layer Sb(110) rhombohedral crystal formed on an Au(111) substrate. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) reveal a pure two-dimensional (2D) Sb stripe structure, composed of a pair of Sb(110) unit cells located in a chiral configuration with mirror symmetry breaking perpendicular to the direction of the bright stripe. Based on angle-resolved photoemission spectroscopy (ARPES) measurements and Sb-weighted band structure from density functional theory calculations, we report the unambiguous determination of Rashba spin-orbit coupled bands from the 2D Sb film, exhibiting a chiral symmetry in the electronic structure with the crossing points located at the $Γ$ point and the X point, respectively. Moreover, From dI/dV spectra and density of states (DOS) calculations, the quantum well (QW) Rashba-type states induced by the in-plane mirror symmetry breaking in the Sb stripe structure have been identified. Orbital decomposition of the projected band structure reveals that hybridization between Sb py states and Au states modifies the spin splitting of the QW states, attributed to the intrinsic strong SOC of Au states introduced into the QW states.

cond-mat.mtrl-sci↗

arXiv2024

Phase Transition of single-layer vanadium diselenide on Au(111) with distinguished electronic structures

Herein, we report the reversible structural transition of single-layer VSe2 grown on Au(111) through alternating thermal annealing and Se replenishment. Using scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), we demonstrate the epitaxial growth of high-quality VSe2 on Au(111) with the octahedral (1T) structure and the Se-vacancy-induced transformation of VSe2 from the metallic moiré (1T) phase to the semiconducting (2H) phase. With convincing agreement between the experimental results and DFT calculations, the nanostructure near the grain boundary in the defective intermediate phase is confirmed, as well as the reaction pathway with Se gradually depleting at elevated temperatures. Importantly, it is revealed that the density of the linear Se defects plays a crucial role in the formation of the 2H domain phase due to the increment of the in-plane lattice parameter after Se desorption and the better thermal stability of the 2H phase compared to the 1T phase. The proper control of the density of Se atoms in the topmost Se layer of VSe2 could feasibly manipulate the ratio between the 1T phase and the 2H phase in the steak-shaped domain, which is regarded as a good platform for 2D homojunctions in nanoelectronics.

cond-mat.mtrl-sci↗

arXiv2023

Achieving unidirectional propagation of twisted magnons in a magnetic nanodisk array

Twisted magnons (TMs) have great potential applications in communication and computing owing to the orbital angular momentum (OAM) degree of freedom. Realizing the unidirectional propagation of TMs is the key to design functional magnonics devices. Here we theoretically study the propagation of TMs in one-dimensional magnetic nanodisk arrays. By performing micromagnetic simulations, we find that the one-dimensional nanodisk array exhibits a few bands due to the collective excitations of TMs. A simple model by considering the exchange interaction is proposed to explain the emerging multiband structure and theoretical results agree well with micromagnetic simulations. Interestingly, for a zigzag structure, the dispersion curves and propagation images of TMs show obvious nonreciprocity for specific azimuthal quantum number ($l$), which originates from a geometric effect depending on the phase difference of TMs and the relative angle between two adjacent nanodisks. Utilizing this feature, one can conveniently realize the unidirectional propagation of TMs with arbitrary nonzero $l$. Our work provides important theoretical references for controlling the propagation of TMs.

cond-mat.mes-hall↗

arXiv2021

Magnetodynamic properties of dipole-coupled 1D magnonic crystals

Magnonic crystals are magnetic metamaterials, that provide a promising way to manipulate magnetodynamic properties by controlling the geometry of the patterned structures. Here, we study the magnetodynamic properties of 1D magnonic crystals consisting of parallel NiFe strips with different strip widths and separations. The strips couple via dipole-dipole interactions. As an alternative to experiments and/or micromagnetic simulations, we investigate the accuracy of a simple macrospin model. For the case of simple strips, a model with a single free parameter to account for an overestimation of the out-of-plane demagnetization of the magnonic lattice is described. By adjusting this parameter a good fit with experimental as well as micromagnetic results is obtained. Moreover, the Gilbert damping is found independent of the lattice constant however the inhomogeneous linewidth broadening found to increase with decreasing stripe separation.

cond-mat.mes-hall↗

arXiv2021

Nonreciprocal Emergence of Hybridized Magnons in magnetic thin Films

We investigate the transfer and control of nonreciprocity through magnons themselves in permalloy thin films deposited on surface oxide silicon substrate. Evidences of nonreciprocal emergence of hybridized dipole exchange magnons (spin waves) at two permalloy surfaces are provided by studying magnon transmission and asymmetry, via Brillouin light scattering measurements. The dipole dominated spin wave and exchange dominated spin wave are found to be localized near the top and bottom surfaces, respectively, and traveling along opposite directions. The nonreciprocity and the localization are intertwined and ca n be tuned by an in plane magnetic field. The effects are well explained by the magnetostatic theory and can be quantitatively reproduced by the micromagnetic simulations. Our findings provide a simple and flexible approach to nonreciprocal all magnon logi c devices with highly compatible with silicon based integrated circuit technology.

cond-mat.mes-hall↗

arXiv2020

Backward magnetostatic surface spin waves in exchange coupled Co/FeNi bilayers

Propagation of backward magnetostatic surface spin waves (SWs) in exchange coupled Co/FeNi bilayers are studied by using Brillouin light scattering (BLS) technique. Two types of SWs modes were identified in our BLS measurements. They are magnetostatic surface waves (MSSWs) mode and perpendicular standing spin waves (PSSWs) mode. The dispersion relations of MSSWs obtained from the Stokes and Anti-Stokes measurements display respectively positive and negative group velocities. The Anti-Stokes branch with positive phase velocities and negative group velocities, known as backward magnetostatic surface mode originates from the magnetostatic interaction of the bilayer. The experimental data are in good agreement with the theoretical calculations. Our results are useful for understanding the SWs propagation and miniaturizing SWs storage devices.

cond-mat.mes-hall↗