Fermionic bound states on a one-dimensional lattice

We study bound states of two fermions with opposite spins in an extended Hubbard chain. The particles interact when located both on a site or on adjacent sites. We find three different types of bound states. Type U is predominantly formed of basis states with both fermions on the same site, while two states of type V originate from both fermions occupying neighbouring sites. Type U, and one of the states from type V, are symmetric with respect to spin flips. The remaining one from type V is antisymmetric. V-states are characterized by a diverging localization length below some critical wave number. All bound states become compact for wave numbers at the edge of the Brilloin zone.Comment: 4 pages, 3 figure

Erratum: On the nonlinear dynamics of electro-magnon excitations in the BaTiO

Original article: EPL, 122 (2018) 6800

On the nonlinear dynamics of electro-magnon excitations in the BaTiO3/Fe nanostructured multiferroic composite material

We study the motion of an electric excitation between the ferroelectric (FE) and the ferromagnetic (FM) components of a MultiFerroic (MF) composite material by analysing the transfer of energy from the FE side to the FM one. The transmission process of the electric excitation, which has an envelope soliton shape, is studied for a one-dimensional model of the barium titanate/iron (BaTiO3/Fe) composite. From the transmission spectrum, we determine the most favourable range of the values of the amplitude and of the width of the initial excitation for the transmission of the FE energy to the FM part of the MF material. From the numerical analysis, it is shown that the position in which we excite the FE component strongly impacts on the solitary wave dynamics. We have also realised that, for some initial positions and suitable range of values of the amplitude and width of the excitation of the polarization, we get a stationary localised magnetic excitation in the FM part of the MF material that lasts for a long time. Such a phenomenon, which originates from a curvilinear trajectory of the incoming excitation is promising enough for the implementation of non-volatile memories based on MF composite materials

Nonlinear dynamics for magnetic systems with a single-spin potential with variable shapes

Results of computer simulations to investigate the spin dynamics of a classical ferromagnet subject to easy-plane anisotropy and a parameterized Zeeman energy are reported. The variability of the Zeeman term induces a deformable substrate potential in the system. The results show substantial deviations between the conventional sine-Gordon and deformable sine-Gordon description. Solitary-like solutions, shock waves, nanopteron waves and a variety of phenomena, including large easy-plane deviations are also observed. The results display ballistic, diffusive as well as stochastic behaviors. The region of parameters and limits of applicability of deformability effects induced by parameterization of the Zeeman energy are examined. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005

Quantum breathers in a finite Heisenberg spin chain with antisymmetric interactions

A study of the likelihood of quantum breathers in a quantum Heisenberg spin system including a Dzyaloshinsky-Moriya interaction (DMI) is done through an extended Bose-Hubbard model while using the scheme of few body physics. The energy spectrum of the resulting Bose-Hubbard Hamiltonian, on a periodic one-dimensional lattice containing more than two quanta shows interesting detailed band structures. From a non degenerate, and a degenerate perturbation theory in addition to a numerical diagonalization, a careful investigation of these fine structures is set up. The attention is focussed on the effects of various interactions that are; the DMI, the Heisenberg in-plane (X, Y) as well as the out of plane exchange interaction on the energy spectrum of such a system. The outcome displays a possibility of an energy self-compensation in the system. We also computed the weight function of the eigenstates in direct space and in the space of normal modes. From a perturbation theory it is shown that the interaction between the quanta leads to an algebraic localization of the modified extended states in the normal-mode space of the non-interacting system that are coined quantum q-breathers excitations

Domain wall motion in ferromagnets modelled by a quintic complex Ginzburg-Landau equation

A quintic complex Ginzburg-Landau equation is derived from a Landau-Lifshitz-Gilbert equation and is used to describe the magnetization dynamics in a one-dimensional uni-axial ferromagnet. Trough the use of suitable approximations, we derive the magnetic solitary wave excitations solutions which have pulse-like shapes. Subsequent numerical simulations reveal domain wall propagation

Breather-impurity interactions and modulational instability in a quantum 2D Klein–Gordon chain

We study the breather-impurity interactions and modulational instability in a quantum 2D Klein–Gordon chain. By using the second quantification operators, we transform classical Hamiltonian into its quantum version, through Glauber’s coherent state representation in addition to the multiple-scale method, the 2D nonlinear Schrödinger equation (NLSE) is obtained. This NLSE is analytically solved by adopting the Rayleigh–Ritz variational method. Around impurity’s critical mass, we prove the existence of resonant structure. This critical mass is observed when plotting the frequency spectrum under the effect of the impurity mass and harmonic force constants. The effects of impurity mass and the harmonic force constants are found in the amplitude frequency spectra. When the breather interacts with the impurity, the system exhibit different scenario that are: barrier, well, excitation and chaotic all related to the trapping phenomenon. The modulational instability (MI) which helps to confirm the existence of breather is investigated. We have shown that impurity strength increases the instability regions, and the MI growth rate can be dramatically affected by the impurity mass around the critical value