6 research outputs found
Phase diagram regions deduced for strongly correlated systems via unitary transformation
From known phase diagram regions of different model Hamiltonians describing
strongly correlated systems we deduced new domains of the ground state phase
diagram of the same model by an unitary transformation. Different types of
extended Hubbard Hamiltonians were used for the starting point and the
existence of new stable spin-density wave, charge-density wave, ferromagnetic
state and a paramagnetic insulator is demonstrated. The used procedure itself
is dimension independent
Plaquette operators used in the rigorous study of ground-states of the Periodic Anderson Model in dimensions
The derivation procedure of exact ground-states for the periodic Anderson
model (PAM) in restricted regions of the parameter space and D=2 dimensions
using plaquette operators is presented in detail. Using this procedure, we are
reporting for the first time exact ground-states for PAM in 2D and finite value
of the interaction, whose presence do not require the next to nearest neighbor
extension terms in the Hamiltonian. In order to do this, a completely new type
of plaquette operator is introduced for PAM, based on which a new localized
phase is deduced whose physical properties are analyzed in detail. The obtained
results provide exact theoretical data which can be used for the understanding
of system properties leading to metal-insulator transitions, strongly debated
in recent publications in the frame of PAM. In the described case, the lost of
the localization character is connected to the break-down of the long-range
density-density correlations rather than Kondo physics.Comment: 34 pages, 5 figure
Tc enhancement of a two-band superconductor in an itinerant antiferromagnetic medium
újratöltve - bibKLT0010061