55 research outputs found
Short Range Interaction Effects on the Density of States of Disordered Two Dimensional Crystals with a half--filled band
The Density of electronic States (DoS) of a two--dimensional square lattice
with substitutional impurities is calculated in the presence of short--range
electron--electron interactions. In the middle of the energy band, the Bragg
reflections off the Brillouin zone boundary are shown to lead to additional
quantum corrections to the DoS, the sign of which is opposite to the sign of
the Altshuler--Aronov's logarithmic correction. The resulting quantum
correction to the DoS at half--filling is positive, i.e. the DoS increases
logarithmically as the Fermi energy is approached. However, far from the
commensurate points where the Bragg reflections are suppressed, the negative
logarithmic corrections to the DoS survive.Comment: 5 pages 2 figure
Formation of three-particle clusters in hetero-junctions and MOSFET structures
A novel interaction mechanism in MOSFET structures and
hetero-junctions between the zone electrons of the two-dimensional (2D) gas and
the charged traps on the insulator side is considered. By applying a canonical
transformation, off-diagonal terms in the Hamiltonian due to the trapped level
subsystem are excluded. This yields an effective three-particle attractive
interaction as well as a pairing interaction inside the 2D electronic band. A
type of Bethe- Goldstone equation for three particles is studied to clarify the
character of the binding and the energy of the three-particle bound states. The
results are used to offer a possible explanation of the Metal-Insulator
transition recently observed in MOSFET and hetero-junctions.Comment: 4 page
Mesoscopic fluctuations of the Density of States and Conductivity in the middle of the band of Disordered Lattices
The mesoscopic fluctuations of the Density of electronic States (DoS) and of
the conductivity of two- and three- dimensional lattices with randomly
distributed substitutional impurities are studied. Correlations of the levels
lying above (or below) the Fermi surface, in addition to the correlations of
the levels lying on opposite sides of the Fermi surface, take place at half
filling due to nesting. The Bragg reflections mediate to increase static
fluctuations of the conductivity in the middle of the band which change the
distribution function of the conductivity at half- filling.Comment: 5 pages, 3 figure
Comment on ``Density of States of Disordered Two-Dimensional Crystals with Half-Filled Band''
In a recent letter (PRL 84, 3930 (2000)) Nakhmedov et al. claimed that the
Van Hove singularity at in the density of states (DoS) of the
two-dimensional crystal with half-filled tight-binding band survives the
addition of substitutional impurities. This derivation suffers from several
inconsistencies. We resolve them and show that the DoS at the band center is
finite, as one might naively expect
Exactly solvable model of three interacting particles in an external magnetic field
The quantum mechanical problem of three identical particles, moving in a
plane and interacting pairwise via a spring potential, is solved exactly in the
presence of a magnetic field. Calculations of the pair--correlation function,
mean distance and the cluster area show a quantization of these parameters.
Especially the pair-correlation function exhibits a certain number of maxima
given by a quantum number. We obtain Jastrow pre-factors which lead to an
exchange correlation hole of liquid type, even in the presence of the
attractive interaction between the identical electrons.Comment: 8 pages 3 figure
- …