30 research outputs found
Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot
We study the dynamics of an electron confined in a one-dimensional double
quantum dot in the presence of driving external magnetic fields. The orbital
motion of the electron is coupled to the spin dynamics by spin orbit
interaction of the Dresselhaus type. We derive an effective time-dependent
Hamiltonian model for the orbital motion of the electron and obtain a
synchronization condition between the orbital and the spin dynamics. From this
model we deduce an analytical expression for the Arnold tongue and propose an
experimental scheme for realizing the synchronization of the orbital and spin
dynamics.Comment: 6 figures, 14 page
Pulse and quench induced dynamical phase transition in a chiral multiferroic spin chain
Quantum dynamics of magnetic order in a chiral multiferroic chain is studied.
We consider two different scenarios: Ultrashort terahertz (THz) excitations or
a sudden electric field quench. Performing analytical and numerical exact
diagonalization calculations we trace the pulse induced spin dynamics and
extract quantities that are relevant to quantum information processing. In
particular, we analyze the dynamics of the system chirality, the von Neumann
entropy, the pairwise and the many body entanglement. If the characteristic
frequencies of the generated states are non-commensurate then a partial loss of
pair concurrence occurs. Increasing the system size this effect becomes even
more pronounced. Many particle entanglement and chirality are robust and
persist in the incommensurate phase. To analyze the dynamical quantum
transitions for the quenched and pulsed dynamics we combined the Weierstrass
factorization technique for entire functions and Lanczos exact diagonalization
method. For a small system we obtained analytical results including the rate
function of Loschmidt echo. Exact numerical calculations for a system up to 40
spins confirm phase transition. Quench- induced dynamical transitions have been
extensively studied recently. Here we show that related dynamical transitions
can be achieved and controlled by appropriate electric field pulses.Comment: 13 pages, 10 figures, submitted in PR
Stochastic heating of a molecular nanomagnet
We study the excitation dynamics of a single molecular nanomagnet by static
and pulsed magnetic fields. Based on a stability analysis of the classical
magnetization dynamics we identify analytically the fields parameters for which
the energy is stochastically pumped into the system in which case the
magnetization undergoes diffusively and irreversibly a large angle deflection.
An approximate analytical expression for the diffusion constant in terms of the
fields parameters is given and assessed by full numerical calculations.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Magnetoelectric fractals, Magnetoelectric parametric resonance and Hopf bifurcation
In the present work, we study the dynamics of a magnetic nanoparticle coupled
through the magnetoelectric coupling to the ferroelectric crystal. The model of
our interest is nonlinear, and we explore the problem under different limits of
weak and strong linearity. By applying two electric fields with different
frequencies, we control the form of the confinement potential of the
ferroelectric subsystem and realize different types of dynamics. We proved that
the system is more sensitive to magnetoelectric coupling in the case of
double-well potential. In particular, in the case of strong nonlinearity,
arbitrary small values of magnetoelectric coupling lead to chaotic dynamics. In
essence, magnetoelectric coupling plays a role akin to the small perturbations
destroying invariant tors according to the KAM theorem. We showed that
bifurcations in the system are of Hopf's type. We observed the formation of
magnetoelectric fractals in the system. In the limit of weak nonlinearity, we
studied a problem of parametric nonlinear resonance and enhancement of magnetic
oscillations through magnetoelectric coupling