439 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
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
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.
Spin-helical Dirac states in graphene induced by polar-substrate surfaces with giant spin-orbit interaction: a new platform for spintronics
Spintronics, or spin electronics, is aimed at efficient control and
manipulation of spin degrees of freedom in electron systems. To comply with
demands of nowaday spintronics, the studies of electron systems hosting giant
spin-orbit-split electron states have become one of the most important
directions providing us with a basis for desirable spintronics devices. In
construction of such devices, it is also tempting to involve graphene, which
has attracted great attention because of its unique and remarkable electronic
properties and was recognized as a viable replacement for silicon in
electronics. In this case, a challenging goal is to make graphene Dirac states
spin-polarized. Here, we report on absolutely new promising pathway to create
spin-polarized Dirac states based on coupling of graphene and polar-substrate
surface states with giant Rashba-type spin-splitting. We demonstrate how the
spin-helical Dirac states are formed in graphene deposited on the surface of
BiTeCl. This coupling induces spin separation of the originally spin-degenerate
graphene states and results in fully helical in-plane spin polarization of the
Dirac electrons.Comment: 5 pages, 3 figure
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
Spectrum of surface-mode contributions to the excitation probability for electron beam interacting with sharp-edged dielectric wedges
The interaction of a nonrelativistic charged particle beam, travelling
parallel to the surface of a sharp-edged dielectric wedge is analyzed. The
general expressions for excitation probability are obtained for a beam moving
along the direction of a symmetry axis, either outside or inside the dielectric
wedge. The dielectric function of the medium is assumed to be isotropic, and
numerical results are given for the materials of experimental interest.Comment: LaTeX 2.09, 15 pages, 10 figure
Inelastic decay rate of quasiparticles in a two-dimensional spin-orbit coupled electron system
We present a study of the inelastic decay rate of quasiparticles in a
two-dimensional electron gas with spin-orbit interaction. The study is done
within the G0W0 approximation. The spin-orbit interaction is taken in the most
general form that includes both Rashba and Dresselhaus contributions linear in
magnitude of the electron 2D momentum. Spin-orbit interaction effect on the
inelastic decay rate is examined at different parameters characterizing the
interaction strength in the electron gas.Comment: 5 pages, 4 figure
Non-Dirac topological surface states in (SnTe)(BiTe)
A new type of topological spin-helical surface states was discovered in
layered van der Waals bonded (SnTe)(BiTe) compounds
which comprise two covalently bonded band inverted subsystems, SnTe and
BiTe, within a building block. This novel topological states
demonstrate non-Dirac dispersion within the band gap. The dispersion of the
surface state has two linear sections of different slope with shoulder feature
between them. Such a dispersion of the topological surface state enables
effective switch of the velocity of topological carriers by means of applying
an external electric field
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