Search results for "waves"

2015

The dynamics of emergent magnetic quasiparticles, such as vortices, domain walls, and bubbles are studied by scanning transmission x-ray microscopy (STXM), combining magnetic (XMCD) contrast with about 25 nm lateral resolution as well as 70 ps time resolution. Essential progress in the understanding of magnetic vortex dynamics is achieved by vortex core reversal observed by sub-GHz excitation of the vortex gyromode, either by ac magnetic fields or spin transfer torque. The basic switching scheme for this vortex core reversal is the generation of a vortex-antivortex pair. Much faster vortex core reversal is obtained by exciting azimuthal spin wave modes with (multi-GHz) rotating magnetic fie…

Image charge dynamics in time-dependent quantum transport

2012

In this work we investigate the effects of the electron-electron interaction between a molecular junction and the metallic leads in time-dependent quantum transport. We employ the recently developed embedded Kadanoff-Baym method [Phys. Rev. B 80, 115107 (2009)] and show that the molecule-lead interaction changes substantially the transient and steady-state transport properties. We first show that the mean-field Hartree-Fock (HF) approximation does not capture the polarization effects responsible for the renormalization of the molecular levels neither in nor out of equilibrium. Furthermore, due to the time-local nature of the HF self-energy there exists a region in parameter space for which …

Frequency-dependent conductivity of UPd2Al3 films

1998

The transmission of UPd2Al3 films was studied (4 K < T < 300 K) in the frequency range from 4 to 32 cm−1 by using a coherent source interferometer which allows for measuring both, amplitude and phase. In addition we report on radio frequency and optical measurements. Below 20 K the conductivity and dielectric constant show strong deviations from the behavior of a normal metal which cannot simply be explained by a single renormalized Drude model with an enhanced mass and reduced scattering rate. Instead, we find evidence for the opening of a pseudogap with a gap energy of 6 cm−1 and an extremely narrow ω = 0 mode which is responsible for the large DC conductivity.

Quasiparticle interference of spin momentum locked surface states at step edges on Re(0001)

2020

Quasiparticle interference patterns formed by a surface state on the Re(0001) surface were investigated using scanning tunneling spectroscopy. The energy dispersion is inferred from Fourier-transformed differential conductivity maps for occupied and unoccupied states. The band dispersion for occupied states agrees with earlier published results obtained by angle-resolved photoemission spectroscopy. An analysis of the phase of interference patterns at step edges reveals a drastic change in the effective energy barrier for backscattering above and below the Fermi level. The attenuation of the interference pattern with increasing distance indicates interband scattering is the dominant scatteri…

Orbital origin and matrix element effects in the Ag/Si(111)-()R30° Fermi surface

2007

The Fermi surface (FS) of the Ag/Si(1 1 1)-3×3 reconstruction with an excess of Ag has been mapped by angle resolved photoemission spectroscopy with polarized light in a wide region of the reciprocal space and with different detection geometries. In contrast to previous results, a strong polarization dependence is observed. Applying the dipole selection rules, it is found that the surface state at the Fermi level, S1 state, has odd symmetry with respect to the mirror plane of the honeycomb-chained triangle structure, indicating that it is mainly derived from Ag 5px and 5py orbitals. This conclusion is revised in the new frame of a inequivalent-triangle structure for the Ag/Si(1 1 1)-3×3 at …

Can the Double Exchange Cause Antiferromagnetic Spin Alignment?

2020

The effect of the double exchange in a square-planar mixed-valence dn+1&minus

Stability of soliplasmon excitations at metal/dielectric interfaces

2011

We show the stability features of different families of soliplasmon excitations by analyzing their different propagation patterns under random perturbations of the initial profile. The role of phase and dispersive waves is also unveiled.

Transmission of electrons through ferromagnetic material and applications to detection of electron spin polarization

1993

The salient features of the total low energy inelastic electron scattering cross section in transition metals are described by a constant term σ 0 plus a term σ d that is proportional to the number of unoccupied d-orbitals. This simple model predicts that low energy electrons transmitted through a ferromagnetic ultrathin film acquire a transport spin polarization a(x). Using the ratio σ 0 /σ d as the only adjustable parameter, the model predicts the enhancement of the spin polarization of the low energy cascade electrons as well as a(x) in reasonable agreement with the existing observations on Fe, Co and Ni. A detector for electron spin polarization P based on the spin dependent transmissio…

Radiation resonant transmission and reflection by a thin layer of an anisotropic plasma

2005

The possibility of radiation resonant transmission and reflection by a thin layer of a plasma possessing an anisotropic electron velocity distribution strongly elongated in the direction of the incident wave polarization is established.

Vortex solitons in photonic crystal fibers

2003

We demonstrate the existence of vortex soliton solutions in photonic crystal fibers. We analyze the role played by the photonic crystal fiber defect in the generation of optical vortices. An analytical prediction for the angular dependence of the amplitude and phase of the vortex solution based on group theory is also provided. Furthermore, all the analysis is performed in the non-paraxial regime.