2 research outputs found
Breakdown of Luttinger's theorem in two-orbital Mott insulators
An analysis of Luttinger's theorem shows that -- contrary to recent claims --
it is not valid for a generic Mott insulator. For a two-orbital Hubbard model
with two electrons per site the crossover from a non-magnetic correlated
insulating phase (Mott or Kondo insulator) to a band insulator is investigated.
Mott insulating phases are characterized by poles of the self-energy and
corresponding zeros in the Greens functions defining a ``Luttinger surface''
which is absent for band insulators. Nevertheless, the ground states of such
insulators with two electrons per unit cell are adiabatically connected.Comment: published version, some formulations change
Some remarks about pseudo gap behavior of nearly antiferromagnetic metals
In the antiferromagnetically ordered phase of a metal, gaps open on parts of
the Fermi surface if the Fermi volume is sufficiently large. We discuss simple
qualitative and heuristic arguments under what conditions precursor effects,
i.e. pseudo gaps, are expected in the paramagnetic phase of a metal close to an
antiferromagnetic quantum phase transition. At least for weak interactions, we
do not expect the formation of pseudo gaps in a three dimensional material.
According to our arguments, the upper critical dimension d_c for the formation
of pseudo gaps is d_c=2. However, at the present stage we cannot rule out a
higher upper critical dimension, 2 < d_c <= 3. We also discuss briefly the role
of statistical interactions in pseudo gap phases.Comment: 6 pages, accepted in PRB, relevant references added, several small
change