arXiv subjects

A. Garcia-Martin

Publications and source records attributed to A. Garcia-Martin.

12 recordsLinked to original sources

arXiv2015

Light localisation and magneto-optic enhancement in Ni anti-dot arrays

The excitation of surface plasmons in magnetic nano-structures can strongly influence their magneto-optical properties. Here, we use photoemission electron microscopy to map the spatial distribution of the electric near-field on a nano-patterned magnetic surface that supports plasmon polaritons. By using different photon energies and polarization states of the incident light we reveal that the electric near-field is either concentrated in spots forming a hexagonal lattice with the same symmetry as the Ni nano-pattern or in stripes oriented along the $Γ$-K direction of the lattice and perpendicular to the polarization direction. We show that the polarization-dependent near-field enhancement on the patterned surface is directly correlated to both the excitation of surface plasmon polaritons on the patterned surface as well as the enhancement of the polar magneto-optical Kerr effect.

cond-mat.mes-hall↗

arXiv2014

Extraordinary transverse magneto-optical Kerr effect in a superlens

It has been shown that a slab of a negative index material can behave as a superlens enhancing the imaging resolution beyond the wavelength limit. We show here that if such a slab possesses in addition some magneto-optical activity, it could act as an ideal optical filter and exhibit an extraordinary transverse magneto-optical Kerr effect. Moreover, we show that losses, which spoil the imaging resolution of these lenses, are a necessary ingredient to observe this effect.

physics.optics↗

arXiv2012

Generalized scattering-matrix approach for magneto-optics in periodically patterned multilayer systems

We present here a generalization of the scattering-matrix approach for the description of the propagation of electromagnetic waves in nanostructured magneto-optical systems. Our formalism allows us to describe all the key magneto-optical effects in any configuration in periodically patterned multilayer structures. The method can also be applied to describe periodic multilayer systems comprising materials with any type of optical anisotropy. We illustrate the method with the analysis of a recent experiment in which the transverse magneto-optical Kerr effect was measured in a Fe film with a periodic array of subwavelength circular holes. We show, in agreement with the experiments, that the excitation of surface plasmon polaritons in this system leads to a resonant enhancement of the transverse magneto-optical Kerr effect.

physics.optics↗

arXiv2009

Magnetooptic enhancement and magnetic properties in Fe antidot films with hexagonal symmetry

The magnetooptic and magnetic properties of hexagonal arrays of holes in optically thin iron films are presented. We analyze their dependence on the hole radius and compare the results to a continuous iron film of same thickness. We observe a large enhancement of the magnetooptic Kerr rotation with respect to that of the continuous film, at frequecies where surface plasmons excitations are expected. Additional simulations are in very good agreement with the experiment and thus confirm the effect of the surface plasmons on the Kerr rotation. The altering of the magnetic properties by the hole array is also visible in the hysteretic behavior of the sample where a dramatic change is observed.

cond-mat.mes-hall↗

arXiv2009

Exchange bias in laterally oxidized Au/Co/Au nanopillars

Au/Co/Au nanopillars fabricated by colloidal lithography of continuous trilayers exhibit and enhanced coercive field and the appearance of an exchange bias field with respect to the continuous layers. This is attributed to the lateral oxidation of the Co interlayer that appears upon disc fabrication. The dependence of the exchange bias field on the Co nanodots size and on the oxidation degree is analyzed and its microscopic origin clarified by means of Monte Carlo simulations based on a model of a cylindrical dot with lateral core/shell structure.

cond-mat.mtrl-sci↗

arXiv2002

Non-analyticity in the distribution of conductances in quasi one dimensional wires

We show that the distribution P(g) of conductances g of a quasi one dimensional wire has non-analytic behavior in the insulating region, leading to a discontinuous derivative in the distribution near g=1. We give analytic expressions for the full distribution and extract an approximate scaling behavior valid for different strengths of disorder close to g=1.

cond-mat.dis-nn↗

arXiv2002

Quantum Conductance in Semimetallic Bismuth Nanocontacts

Electronic transport properties of bismuth nanocontacts are analyzed by means of a low temperature scanning tunneling microscope. The subquantum steps observed in the conductance versus elongation curves give evidence of atomic rearrangements in the contact. The underlying quantum nature of the conductance reveals itself through peaks in the conductance histograms. The shape of the conductance curves at 77 K is well described by a simple gliding mechanism for the contact evolution during elongation. The strikingly different behaviour at 4 K suggests a charge carrier transition from light to heavy ones as the contact cross section becomes sufficiently small.

cond-mat.mes-hall↗

arXiv2001

Universal Conductance Distributions in the Crossover between Diffusive and Localization Regimes

The full distribution of the conductance $P(G)$ in quasi-one-dimensional wires with rough surfaces is analyzed from the diffusive to the localization regime. In the crossover region, where the statistics is dominated by only one or two eigenchannels, the numerically obtained P(G) is found to be independent of the details of the system with the average conductance as the only scaling parameter. For < e^2/h, P(G) is given by an essentially ``one-sided'' log-normal distribution. In contrast, for e^2/h < <= 2e^2/h, the shape of P(G) remarkable agrees with those predicted by random matrix theory for two fluctuating transmission eigenchannels.

cond-mat.dis-nn↗

arXiv2001

Resonant radiation pressure on neutral particles in a waveguide

A theoretical analysis of electromagnetic forces on neutral particles in an hollow waveguide is presented. We show that the effective scattering cross section of a very small (Rayleigh) particle can be strongly modified inside a waveguide. The coupling of the scattered dipolar field with the waveguide modes induce a resonant enhanced backscattering state of the scatterer-guide system close to the onset of new modes. The particle effective cross section can then be as large as the wavelength even far from any transition resonance. As we will show, a small particle can be strongly accelerated along the guide axis while being highly confined in a narrow zone of the cross section of the guide.

physics.optics↗

arXiv1998

Statistical Distribution of Intensities Reflected from Disordered Media

A theoretical analysis of the statistical distributions of the reflected intensities from random media is presented. We use random matrix theory to analytically deduce the probability densities in the localization regime. Numerical calculations of the coupling to backward modes in surface corrugated waveguides are also put forward for comparison. Interestingly, the speckle distributions are found to be independent of the transport regime. Despite the scattering being highly non-isotropic, the predicted probability densities reproduce accurately the numerical results.

cond-mat.dis-nn↗

arXiv1998

Intensity Distribution of Modes in Surface Corrugated Waveguides

Exact calculations of transmission and reflection coefficients in surface randomly corrugated optical waveguides are presented. As the length of the corrugated part of the waveguide increases, there is a strong preference to forward coupling through the lowest mode. An oscillating behavior of the enhanced backscattering as a function of the wavelength is predicted. Although the transport is strongly non isotropic, the analysis of the probability distributions of the transmitted waves confirms in this configuration distributions predicted by Random Matrix Theory for volume disorder.

cond-mat.dis-nn↗

arXiv1998

Transition from Diffusive to Localized Regimes in Surface Corrugated Optical Waveguides

Exact calculations of the transmittance of surface corrugated optical waveguides are presented. The elastic scattering of diffuse light or other electromagnetic waves from a rough surface induces a diffusive transport along the waveguide axis. As the length of the corrugated part of the waveguide increases, a transition from the diffusive to the localized regime is observed. This involves an analogy with electron conduction in nanowires, and hence, a concept analogous to that of ``resistance'' can be introduced. We show an oscillatory behavior of both the elastic mean free path and the localization length versus the wavelength.

cond-mat.mes-hall↗