Séminaire du LPTMS : Daniel Cabra (La Plata)

Zoom Link: https://cnrs.zoom.us/j/97529623199?pwd=Tm9tLy8vUUZDY2tqQmpNQnZFRTlqdz09

Meeting ID: 975 2962 3199
Passcode: 1kCW7x

We propose a microscopic magneto-electric model in which the coupling between spins
and electric dipoles is mediated by lattice distortions. The magnetic sector is described
by a Heisenberg model coupled directly to the lattice via a standard spin-Peierls term and

indirectly to the electric dipole variables via the distortion of the surrounding electronic clouds.

Electric dipoles are described by Ising variables for simplicity. We show that the effective

magneto-electric coupling which arises due to the interconnecting lattice deformations is

quite efficient in one-dimensional arrays. More precisely, we show using bosonization and

extensive DMRG numerical simulations that by increasing the magnetic field above the spin

Peierls gap, a massive polarization switch-off occurs due to the proliferation of soliton pairs.

Introducing further neighbors couplings and single ion anisotropy, the system also shows the

« uudd » (or so-called antiphase) magnetic ordering observed in several type II multiferroic materials.

We also discuss recent results for a two-dimensional generalization.