3 research outputs found
Asymptotically exact dispersion relations for collective modes in a confined charged Fermi liquid
Using general local conservations laws we derive dispersion relations for
edge modes in a slab of electron liquid confined by a symmetric potential. The
dispersion relations are exact up to , where is a wave
vector and is an effective screening length. For a harmonic external
potential the dispersion relations are expressed in terms of the {\em exact}
static pressure and dynamic shear modulus of a homogeneous liquid with the
density taken at the slab core. We also derive a simple expression for the
frequency shift of the dipole (Kohn) modes in nearly parabolic quantum dots in
a magnetic field.Comment: RevTeX4, 4 pages. Revised version with new results on quantum qots
and wires. Published in Phys.Rev.
Collisionless hydrodynamics for 1D motion of inhomogeneous degenerate electron gases: equivalence of two recent descriptions
Recently I. Tokatly and O. Pankratov (''TP'', Phys. Rev. B 60, 15550 (1999))
used velocity moments of a semiclassical kinetic equation to derive a
hydrodynamic description of electron motion in a degenerate electron gas.
Independently, the present authors (Theochem 501-502, 327 (2000)) used
considerations arising from the Harmonic Potential Theorem (Phys. Rev. Lett.
73, 2244 (1994)) to generate a new form of high-frequency hydrodynamics for
inhomogeneous degenerate electron gases (HPT-N3 hydrodynamics). We show here
that TP hydrodynamics yields HPT-N3 hydrodynamics when linearized about a
Thomas-Fermi groundstate with one-dimensional spatial inhomnogeneity.Comment: 17p
Intersubband spin-density excitations in quantum wells with Rashba spin splitting
In inversion-asymmetric semiconductors, spin-orbit coupling induces a
k-dependent spin splitting of valence and conduction bands, which is a
well-known cause for spin decoherence in bulk and heterostructures.
Manipulating nonequilibrium spin coherence in device applications thus requires
understanding how valence and conduction band spin splitting affects carrier
spin dynamics. This paper studies the relevance of this decoherence mechanism
for collective intersubband spin-density excitations (SDEs) in quantum wells. A
density-functional formalism for the linear spin-density matrix response is
presented that describes SDEs in the conduction band of quantum wells with
subbands that may be non-parabolic and spin-split due to bulk or structural
inversion asymmetry (Rashba effect). As an example, we consider a 40 nm
GaAs/AlGaAs quantum well, including Rashba spin splitting of the conduction
subbands. We find a coupling and wavevector-dependent splitting of the
longitudinal and transverse SDEs. However, decoherence of the SDEs is not
determined by subband spin splitting, due to collective effects arising from
dynamical exchange and correlation.Comment: 10 pages, 4 figure