724 research outputs found
Nonlinear screening in two-dimensional electron gases
We have performed self-consistent calculations of the nonlinear screening of
a point charge Z in a two-dimensional electron gas using a density functional
theory method. We find that the screened potential for a Z=1 charge supports a
bound state even in the high density limit where one might expect perturbation
theory to apply. To explain this behaviour, we prove a theorem to show that the
results of linear response theory are in fact correct even though bound states
exist.Comment: 4 pages, 4 figure
The role of surface plasmons in the decay of image-potential states on silver surfaces
The combined effect of single-particle and collective surface excitations in
the decay of image-potential states on Ag surfaces is investigated, and the
origin of the long-standing discrepancy between experimental measurements and
previous theoretical predictions for the lifetime of these states is
elucidated. Although surface-plasmon excitation had been expected to reduce the
image-state lifetime, we demonstrate that the subtle combination of the spatial
variation of s-d polarization in Ag and the characteristic non-locality of
many-electron interactions near the surface yields surprisingly long
image-state lifetimes, in agreement with experiment.Comment: 4 pages, 2 figures, to appear in Phys. Rev. Let
Exchange and correlation effects in the relaxation of hot electrons in noble metals
We report extensive first-principles calculations of the inelastic lifetime
of low-energy electrons in the noble metals Cu, Ag, and Au. The quasiparticle
self-energy is computed with full inclusion of exchange and correlation (xc)
effects, in the framework of the GW\Gamma approximation of many-body theory.
Although exchange and correlation may considerably reduce both the screening
and the bare interaction of hot electrons with the Fermi gas, these corrections
have opposite signs. Our results indicate that the overall effect of
short-range xc is small and GW\Gamma linewidths are close to their xc-free
G^0W^0 counterparts, as occurs in the case of a free-electron gas.Comment: 9 pages, 8 figures. To appear in Phys. Rev.
Self-energy and lifetime of Shockley and image states on Cu(100) and Cu(111): Beyond the GW approximation of many-body theory
We report many-body calculations of the self-energy and lifetime of Shockley
and image states on the (100) and (111) surfaces of Cu that go beyond the
approximation of many-body theory. The self-energy is computed in the framework
of the GW\Gamma approximation by including short-range exchange-correlation
(XC) effects both in the screened interaction W (beyond the random-phase
approximation) and in the expansion of the self-energy in terms of W (beyond
the GW approximation). Exchange-correlation effects are described within
time-dependent density-functional theory from the knowledge of an adiabatic
nonlocal XC kernel that goes beyond the local-density approximation.Comment: 8 pages, 5 figures, to appear in Phys. Rev.
Theoretical study of ionization of an alkali atom adsorbed on a metal surface by laser assisted subfemtosecond pulse
The first numerical simulation of the process of ionization of an atom
adsorbed on a metal surface by the subfemtosecond pulse is presented. The
streaking scheme is considered, when a weak sub-femtosecond pulse comes
together with a strong IR pulse with a variable delay between them. The problem
is analyzed with numerical solving the non-stationary Schroedinger equation in
the cylindrical coordinate. The results obtained are compared with ones in the
gas phase. We show that the surface influences the DDCS, but the observation of
this influence, beside the trivial polarization shift of the energy of the
initial state, requires a quite high experimental resolution
Nonlinear screening and stopping power in two-dimensional electron gases
We have used density functional theory to study the nonlinear screening
properties of a two-dimensional (2D) electron gas. In particular, we consider
the screening of an external static point charge of magnitude Z as a function
of the distance of the charge from the plane of the gas. The self-consistent
screening potentials are then used to determine the 2D stopping power in the
low velocity limit based on the momentum transfer cross-section. Calculations
as a function of Z establish the limits of validity of linear and quadratic
response theory calculations, and show that nonlinear screening theory already
provides significant corrections in the case of protons. In contrast to the 3D
situation, we find that the nonlinearly screened potential supports a bound
state even in the high density limit. This behaviour is elucidated with the
derivation of a high density screening theorem which proves that the screening
charge can be calculated perturbatively in the high density limit for arbitrary
dimensions. However, the theorem has particularly interesting implications in
2D where, contrary to expectations, we find that perturbation theory remains
valid even when the perturbing potential supports bound states.Comment: 23 pages, 15 figures in RevTeX
Ultrafast electron dynamics in metals
During the last decade, significant progress has been achieved in the rapidly
growing field of the dynamics of {\it hot} carriers in metals. Here we present
an overview of the recent achievements in the theoretical understanding of
electron dynamics in metals, and focus on the theoretical description of the
inelastic lifetime of excited hot electrons. We outline theoretical
formulations of the hot-electron lifetime that is originated in the inelastic
scattering of the excited {\it quasiparticle} with occupied states below the
Fermi level of the solid. {\it First-principles} many-body calculations are
reviewed. Related work and future directions are also addressed.Comment: 17 pages, two columns, 13 figures, to appear in ChemPhysChe
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
-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 () electrons. In aluminum, a simple metal with no -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.Comment: 4 papes, 2 figures, to appear in Phys. Rev. Let
- …