arXiv subjects

I. Campillo

Publications and source records attributed to I. Campillo.

13 recordsLinked to original sources

arXiv2005

Site and lattice resonances in metallic hole arrays

A powerful analytical approach is followed to study light transmission through subwavelength holes drilled in thick perfect-conductor films, showing that full transmission (100%) is attainable in arrays of arbitrarily narrow holes as compared to the film thickness. The interplay between resonances localized in individual holes and lattice resonances originating in the array periodicity reveals new mechanisms of transmission enhancement and suppression. In particular, localized resonances obtained by filling the holes with high-index-of-refraction material are examined and experimentally observed through large enhancement in the transmission of individual holes.

cond-mat.mtrl-sci↗

arXiv2004

Enhanced millimiter wave transmission through subwavelength hole arrays

In this letter we explore, both experimentally and theoretically, the existence in the millimeter wave range of the phenomenon of extraordinary light transmission though arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by using an AB Millimetre Quasioptical Vector Network Analyzer in the wavelength range between 4.2mm to 6.5mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra.

cond-mat.mtrl-sci↗

arXiv2001

Lifetime of d-holes at Cu surfaces: Theory and experiment

We have investigated the hole dynamics at copper surfaces by high-resolution angle-resolved photoemission experiments and many-body quasiparticle GW calculations. Large deviations from a free-electron-like picture are observed both in the magnitude and the energy dependence of the lifetimes, with a clear indication that holes exhibit longer lifetimes than electrons with the same excitation energy. Our calculations show that the small overlap of d- and sp-states below the Fermi level is responsible for the observed enhancement. Although there is qualitative good agreement of our theoretical predictions and the measured lifetimes, there still exist some discrepancies pointing to the need of a better description of the actual band structure of the solid.

cond-mat.str-el↗

arXiv2001

Dynamic structure factor of gold

We have investigated the role of localized {\it d} bands in the dynamical response of Au, on the basis of {\it ab initio} pseudopotential calculations. The density-response function has been evaluated in the random-phase approximation. For small momenta, we have found a double peak structure in the energy-loss function, which results from the presence of {\it d} electrons. These results are in good agreement with the experimentally determined optical response of gold. We also analyze the dependence of the dynamical structure factor on the wave vector {\bf q}.

cond-mat.mtrl-sci↗

arXiv2000

Hole dynamics in noble metals

We present a detailed analysis of hole dynamics in noble metals (Cu and Au), by means of first-principles many-body calculations. While holes in a free-electron gas are known to live shorter than electrons with the same excitation energy, our results indicate that d-holes in noble metals exhibit longer inelastic lifetimes than excited sp-electrons, in agreement with experiment. The density of states available for d-hole decay is larger than that for the decay of excited electrons; however, the small overlap between d- and sp-states below the Fermi level increases the d-hole lifetime. The impact of d-hole dynamics on electron-hole correlation effects, which are of relevance in the analysis of time-resolved two-photon photoemission experiments, is also addressed.

cond-mat.mtrl-sci↗

arXiv2000

The role of occupied d states in the relaxation of hot electrons in Au

We present first-principles calculations of electron-electron scattering rates of low-energy electrons in Au. Our full band-structure calculations indicate that a major contribution from occupied d states participating in the screening of electron-electron interactions yields lifetimes of electrons in Au with energies of $1.0-3.0 {\rm eV}$ above the Fermi level that are larger than those of electrons in a free-electron gas by a factor of $\sim 4.5$. This prediction is in agreement with a recent experimental study of ultrafast electron dynamics in Au(111) films (J. Cao {\it et al}, Phys. Rev. B {\bf 58}, 10948 (1998)), where electron transport has been shown to play a minor role in the measured lifetimes of hot electrons in this material.

cond-mat.mtrl-sci↗

arXiv2000

First-principles calculations of hot-electron lifetimes in metals

First-principles calculations of the inelastic lifetime of low-energy electrons in Al, Mg, Be, and Cu are reported. Quasiparticle damping rates are evaluated from the knowledge of the electron self-energy, which we compute within the GW approximation of many-body theory. Inelastic lifetimes are then obtained along various directions of the electron wave vector, with full inclusion of the band structure of the solid. Average lifetimes are also reported, as a function of the electron energy. In Al and Mg, splitting of the band structure over the Fermi level yields electron lifetimes that are smaller than those of electrons in a free-electron gas. Larger lifetimes are found in Be, as a result of the characteristic dip that this material presents in the density of states near the Fermi level. In Cu, a major contribution from $d$ electrons participating in the screening of electron-electron interactions yields electron lifetimes which are well above those of electrons in a free-electron gas with the electron density equal to that of valence ($4s^1$) electrons.

cond-mat.mtrl-sci↗

arXiv1999

Polarization induced by charged particles in real solids

We report a first-principles description of the induced wake potential and density in real solids. The linear-response formalism is used to obtain the potential and density induced by an external charge penetrating through an inhomogeneous periodic system. The linear dynamical response of the system is evaluated in the random-phase approximation, by including the full band structure of the solid. The impact of the periodic crystalline potential is analyzed, and variations of the wake along different channels in Al and Si are investigated.

cond-mat.mtrl-sci↗

arXiv1999

Band structure effects on the interaction of charged particles with solids

A survey is presented of current investigations of the impact of band structure effects on various aspects of the interaction of charged particles with real solids. The role that interband transitions play in the decay mechanism of bulk plasmons is addressed, and results for plasmon linewidths in Al and Si are discussed. {\it Ab initio} calculations of the electronic energy loss of ions moving in Al and Si are also presented, within linear response theory, from a realistic description of the one-electron band structure and a full treatment of the dynamic electronic response of valence electrons. Both random and position-dependent stopping powers of valence electrons are computed.

cond-mat.mtrl-sci↗

arXiv1999

Inelastic lifetimes of hot electrons in real metals

We report a first-principles description of inelastic lifetimes of excited electrons in real Cu and Al, which we compute, within the GW approximation of many-body theory, from the knowledge of the self-energy of the excited quasiparticle. Our full band-structure calculations indicate that actual lifetimes are the result of a delicate balance between localization, density of states, screening, and Fermi-surface topology. A major contribution from $d$-electrons participating in the screening of electron-electron interactions yields lifetimes of excited electrons in copper that are larger than those of electrons in a free-electron gas with the electron density equal to that of valence ($4s^1$) electrons. In aluminum, a simple metal with no $d$-bands, splitting of the band structure over the Fermi level results in electron lifetimes that are smaller than those of electrons in a free-electron gas.

cond-mat.mtrl-sci↗

arXiv1999

Ab initio calculations of the dynamical response of copper

The role of localized $d$-bands in the dynamical response of Cu is investigated, on the basis of {\em ab initio} pseudopotential calculations. The density-response function is evaluated in both the random-phase approximation (RPA) and a time-dependent local-density functional approximation (TDLDA). Our results indicate that in addition to providing a polarizable background which lowers the free-electron plasma frequency, d-electrons are responsible, at higher energies and small momenta, for a double-peak structure in the dynamical structure factor. These results are in agreement with the experimentally determined optical response of copper. We also analyze the dependence of dynamical scattering cross sections on the momentum transfer.

cond-mat.mtrl-sci↗

arXiv1998

Quadratic response theory for the interaction of charged particles with an electron gas

A survey is presented of the theoretical status of quadratic response theories for the understanding of nonlinear aspects in the interaction of charged particles with matter. In the frame of the many-body perturbation theory we study the interaction of charged particles with the electron gas, within the random-phase approximation (RPA). In particular, nonlinear corrections to the stopping power of an electron gas for ions are analyzed, and special emphasis is made on the contribution to the stopping power coming from the excitation of single and double plasmons. Double plasmon mean free paths of swift electrons passing through an electron gas are also discussed.

cond-mat.mtrl-sci↗

arXiv1998

Electronic stopping power of aluminum crystal

Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are presented, within linear-response theory, from a realistic description of the one-electron band-structure and a full treatment of the dynamical electronic response of valence electrons. For the evaluation of the density-response function we use the random-phase approximation and, also, a time-dependent extension of local-density functional theory. We evaluate both position-dependent and random stopping powers, for a wide range of projectile velocities. Our results indicate that at low velocities band structure effects slightly enhance the stopping power. At velocities just above the threshold velocity for plasmon excitation, the stopping power of the real solid is found to be smaller than that of jellium electrons, corrections being of about 10%. This reduction can be understood from sum rule arguments.

cond-mat.mtrl-sci↗