arXiv subjects

Zai-Dong Li

Publications and source records attributed to Zai-Dong Li.

14 recordsLinked to original sources

arXiv2025

Chirality and polarization of inertial antiferromagnetic resonances driven by spin-orbit torques

It is widely accepted that the handedness of a resonant mode is an intrinsic property. We show that, by tailoring the polarization and handedness of alternating spin-orbit torques used as the driving force, the polarization state and handedness of inertial resonant modes in an antiferromagnet (AFM) can be actively controlled. In contrast with ferromagnets, whose resonant-mode polarization is essentially fixed, AFM inertial modes can continuously evolve from elliptic through circular to linear polarization as the driving polarization is varied. We further identify an inertia-dependent critical degree of driving polarization at which the mode becomes linearly polarized while its handedness reverses.

cond-mat.mes-hall↗

arXiv2018

The high-frequency dynamics of domain walls with strong Dzyaloshinskii-Moriya interaction

Domain walls (DWs) in perpendicularly magnetized nanotracks (PMNTs) with interfacial Dzyaloshinskii-Moriya interaction (DMI) have become the primary objects of theoretical and experimental interest due to their technological suitability in spintronic nanodevices. Chiral DWs in PMNTs can be driven efficiently by the spin-orbit torque. However, the high-frequency dynamic behavior of the chiral DW has not been explored. In this work, using micromagnetic calculation, we have discovered a novel dynamic mode, the sway mode, of DWs under an out-of-plane high-frequency alternating current (AC) magnetic field in a PMNT with strong DMI. This dynamic phenomenon is strictly related with DMI-related boundary effect and can be understood in terms of the propagation of an amplitude-tuned spin wave in the DW plane. The spin wave exhibits some characteristic frequencies due to the space-confinement of DW. This work offers the possibility of a visual route for characterizing DMI.

physics.comp-ph↗

arXiv2015

Quantum Hall Effects in a Non-Abelian Honeycomb Lattice

We study the tunable quantum Hall effects in a non-Abelian honeycomb optical lattice which is a many-Dirac-points system. We find that the quantum Hall effects present different features as change as relative strengths of several perturbations. Namely, a gauge-field-dressed next-nearest-neighbor hopping can induce the quantum spin Hall effect and a Zeeman field can induce a so-called quantum anomalous valley Hall effect which includes two copies of quantum Hall states with opposite Chern numbers and counter-propagating edge states. Our study extends the borders of the field of quantum Hall effects in honeycomb optical lattice when the internal valley degrees of freedom enlarge.

cond-mat.str-el↗

arXiv2013

Inhomogeneous spin domain induced by the quadratic Zeeman effect in spin-1 Bose-Einstein condensate

We show two kinds of inhomogeneous spin domain possessing Néel-like domain walls in spin-1 Bose-Einstein condensate, which are induced by the positive and negative quadratic Zeeman effect (QZE) respectively. In both cases, the spin density distribution is inhomogeneous and has zeros where the magnetization vanishes. For positive and negative QZE, the spin patterns and topological structures are remarkably different. Such phenomena are due to the pointwise different axisymmetry-breaking caused by the pointwise different population exchange between the sublevels, arising uniquely from the QZE. We analyze in detail the inhomogeneous domain formation and related experimental observations for the spin-1 $^{87}$Rb and $^{23}$Na condensate.

cond-mat.quant-gas↗

arXiv2011

Magnetic rogue wave in a perpendicular anisotropic ferromagnetic nanowire with spin-transfer torque

We present the current controlled motion of dynamic soliton embedded in spin wave background in ferromagnetic nanowire. With the stronger breather character we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave is mainly arose from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between envelope soliton and background, and the critical current condition is obtained analytically. Even more interesting is that the spin-transfer torque plays the completely opposite role for the cases of below and above the critical value.

cond-mat.mtrl-sci↗

arXiv2011

Matter rogue wave in Bose-Einstein condensates with attractive atomic interaction

We investigate the matter rogue wave in Bose-Einstein Condensates with attractive interatomic interaction analytically and numerically. Our results show that the formation of rogue wave is mainly due to the accumulation of energy and atoms toward to its central part; Rogue wave is unstable and the decay rate of the atomic number can be effectively controlled by modulating the trapping frequency of external potential. The numerical simulation demonstrate that even a small periodic perturbation with small modulation frequency can induce the generation of a near-ideal matter rogue wave. We also give an experimental protocol to observe this phenomenon in Bose-Einstein Condensates.

cond-mat.quant-gas↗

arXiv2010

Dark Soliton Interaction of Spinor Bose-Einstein Condensates in an Optical Lattice

We study the magnetic soliton dynamics of spinor Bose-Einstein condensates in an optical lattice which results in an effective Hamiltonian of anisotropic pseudospin chain. An equation of nonlinear Schrödinger type is derived and exact magnetic soliton solutions are obtained analytically by means of Hirota method. Our results show that the critical external field is needed for creating the magnetic soliton in spinor Bose-Einstein condensates. The soliton size, velocity and shape frequency can be controlled in practical experiment by adjusting the magnetic field. Moreover, the elastic collision of two solitons is investigated in detail.

cond-mat.other↗

arXiv2010

Hirota method for the nonlinear Schrődinger equation with an arbitrary linear time-dependent potential

In this paper, a Hirota method is developed for applying to the nonlinear Schrödinger equation with arbitrary time-dependent linear potential which denotes the dynamics of soliton solutions in quasi-one-dimensional Bose-Einstein condensation. The nonlinear Schrödinger equation is decoupled to two equations carefully. With a reasonable assumption the one- and two-soliton solutions are constructed analytically in the presence of an arbitrary time-dependent linear potential.

cond-mat.other↗

arXiv2010

Interaction of a nonlinear spin wave and magnetic soliton in a uniaxial anisotropic ferromagnet

We study the interaction of a nonlinear spin-wave and magnetic soliton in a uniaxial anisotropic ferromagnet. By means of a reasonable assumption and a straightforward Darboux transformation one- and two-soliton solutions in a nonlinear spin-wave background are obtained analytically, and their properties are discussed in detail. In the background of a nonlinear spin wave the amplitude of the envelope soliton has the spatial and temporal period, and soliton can be trapped only in space. The amplitude and wave number of spin wave have the different contribution to the width, velocity, and the amplitude of soliton solutions, respectively. The envelope of solution hold the shape of soliton, and the amplitude of each envelope soliton keeps invariability before and after collision which shows the elastic collision of two envelope soliton in the background of a nonlinear spin wave.

cond-mat.other↗

arXiv2010

Nonautonomous solitons of Bose-Einstein condensation in a linear potential with an arbitrary time-dependence

In the presence of a linear potential with an arbitrary time-dependence, Hirota method is developed carefully for applying into the effective mean-field model of quasi-one-dimensional Bose-Einstein condensation with repulsive interaction. We obtain the exact nonautonomous soliton solution (NSS) analytically. These solutions show that the time-dependent potential can affect the velocity of NSS. In some special cases the velocity has the character of both increase and oscillation with time. A detail analysis for the asymptotic behaviour of solutions shows that the collision of two NSSs is elastic.

cond-mat.other↗

arXiv2010

Nonautonomous Bright and Dark Solitons of Bose-Einstein Condensates with Feshbach-Managed Time-Dependent Scattering Length

We present a family of nonautonomous bright and dark soliton solutions of Bose-Einstein condensates with the time-dependent scattering length in an expulsive parabolic potential. These solutions show that the amplitude, width, and velocity of soliton can be manipulated by adjusting the atomic scattering length via Feshbach resonance. For the cases of both attractive and repulsive interaction, the total particles number is a conservation quantity, but the peak (dip) density can be controlled by the Feshbach resonance parameter. Especially, we investigate the modulation instability process in uniform Bose-Einstein condensates with attractive interaction and nonvanishing background, and clarify that the procedure of pattern formation is in fact the superposition of the perturbed dark and bright solitary wave. At last, we give the analytical expressions of nonautonomous dark one- and two-soliton solutions for repulsive interaction, and investigate their properties analytically.

cond-mat.quant-gas↗

arXiv2010

Screw-pitch effect and velocity oscillation of domain-wall in ferromagnetic nanowire driven by spin-polarized current

We investigate the dynamics of domain wall in ferromagnetic nanowire with spin-transfer torque. The critical current condition is obtained analytically. Below the critical current, we get the static domain wall solution which shows that the spin-polarized current can't drive domain wall moving continuously. In this case, the spin-transfer torque plays both the anti-precession and anti-damping roles, which counteracts not only the spin-precession driven by the effective field but also Gilbert damping to the moment. Above the critical value, the dynamics of domain wall exhibits the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width, respectively. Both the theoretical analysis and numerical simulation demonstrate that this novel phenomenon arise from the conjunctive action of Gilbert-damping and spin-transfer torque. We also find that the roles of spin-transfer torque are entirely contrary for the cases of below and above the critical current.

cond-mat.other↗

arXiv2010

Domain-wall solutions of spinor Bose-Einstein condensates in an optical lattice

We studied the static and dynamic domain wall solutions of spinor Bose-Einstein condensates trapped in an optical lattice. The single and double domain wall solutions are constructed analytically. Our results show that the magnetic field and light-induced dipolar interactions play an important role for both the formation of different domain walls and the adjusting of domain wall width and velocity. Moreover, these interactions can drive the motion of domain wall of Bose ferromagnet systems similar to that driven by the external magnetic field or the spin-polarized current in fermion ferromagnet.

cond-mat.other↗

arXiv2007

Soliton Solution for the Spin Current in Ferromagnetic Nanowire

We investigate the interaction of a periodic solution and one-soliton solution for the spin-polarized current in a uniaxial ferromagnetic nanowire. The amplitude and wave number of the periodic solution for the spin current have the different contribution to the width, velocity, and the amplitude of soliton solution, respectively. Moreover, we found that the soliton can be trapped only in space with a proper condition. At last we analyze the modulation instability and discuss dark solitary wave propagation for the spin current on the background of a periodic solution. In some special cases the solution can be expressed by the linear combination of periodic solution and soliton solution.

cond-mat.other↗