Spin waves in doped graphene: A time-dependent spin density functional approach to collective excitations in paramagnetic two-dimensional Dirac fermion gases

Collective Excitations of Dirac Electrons in Graphene

Two-dimensional electrons in graphene are known to behave as massless fermions with Dirac-Weyl type linear dispersion near the Dirac crossing points. We have investigated the collective excitations of this system in the presence or absence of an external magnetic field. Unlike in the conventional two-dimensional electron system, the ν = 1 m fractional quantum Hall state in graphene was found to...

Spin dynamics from time-dependent spin-density-functional theory.

We derive the spin-wave dynamics of a magnetic material from the time-dependent spin-density-functional theory in the linear response regime. The equation of motion for the magnetization includes, besides the static spin stiffness, a "Berry curvature" correction and a damping term. A gradient expansion scheme based on the homogeneous spin-polarized electron gas is proposed for the latter two qu...

Coupling of spin waves with charge- and spin-density excitations in spin-polarized quantum wells

The coupling of spin waves with chargeand spin-density waves is shown to be induced by a spin-dependent interaction in a quantum well, which is spin polarized by a dc magnetic field at an angle u to the symmetry axis. The mixing of the plasmonic and magnonic modes, which occurs for both intraand intersubband transitions, depends on the coupling constant of the spin-spin interaction, the tilt an...

Long-wavelength collective excitations in a two-dimensional spin-polarized electron gas: A phenomenological theory

The dispersion relations of the collective excitations induced in a 2D spin-polarized electron gas are derived within the framework of the Landau-Silin theory applied to a two-component Fermi liquid. The quasiparticle interaction is described by spin-dependent coefficients, which are parametric functions of the initial degree of polarization. The motion of the low-energy excitations satisfies a...

Unconventional spin-density waves in dipolar Fermi gases