Defect-Induced Hedgehog Polarization States in Multiferroics

Polarization-induced switching effect in graphene nanoribbon edge-defect junction.

With nonequilibrium Green's function approach combined with density functional theory, we perform an ab initio calculation to investigate transport properties of graphene nanoribbon (GNR) junctions self-consistently. Tight-binding approximation is applied to model the zigzag (ZGNR) electrodes, and its validity is confirmed in comparison to the GAUSSIAN03 periodic boundary condition calculation ...

Interpreting current-induced spin polarization in topological insulator surface states

Motivated by recent experiments, we address an ambiguity between the intrinsic in-plane spin projection of 2-dimensional surface states on 3-dimensional topological insulators and their ensemble spin polarization induced by a non-equilibrium charge current. Standard expressions from a Boltzmann equation approach in the relaxation-time approximation at zero and finite temperature are used to emp...

Electric field control of magnon-induced magnetization dynamics in multiferroics

We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magni...

Vacuum polarization by a composite topological defect

In this paper we analyze one-loop quantum effects of a scalar field induced by a composite topological defect consisting a cosmic string on a p-dimensional brane and a (m+ 1)dimensional global monopole in the transverse extra dimensions. The corresponding Green function is presented as a sum of two terms. The first one corresponds to the bulk where the cosmic string is absent and the second one...

Electromagnon excitations in canted-spin multiferroics