2 research outputs found
Low-energy effective representation of the Gutzwiller-projected BCS Hamiltonian close to half filling
We investigate analytically a connection between the t-J model and the
strongly correlated Bardeen-Cooper-Schrieffer (BCS) Hamiltonian, with the
effect of strong electron correlations accounted by the Gutzwiller projection.
We show that in the immediate vicinity of half filling the projected 2D BCS
Hamiltonian with strong pairing develops an antiferromagnetically (AF) ordered
ground state. This result explicitly demonstrates that antiferromagnetism in
this model appears as a natural consequence of the strong Coulomb repulsion in
a low doped regime. At moderate doping the ground state of the
Gutzwiller-projected BCS Hamiltonian becomes qualitatively similar to
Anderson's resonating valence bond state which is known to fit nicely the
properties of the t-J model in this regime. These two properties taken together
indicate that the projected BCS Hamiltonian captures the essential low-energy
physics of the t-J model in the whole underdoped region
Doped carrier formulation of the t-J model: the projection constraint and the effective Kondo-Heisenberg lattice representation
We show that the recently proposed doped carrier Hamiltonian formulation of
the t-J model should be complemented with the constraint that projects out the
unphysical states. With this new important ingredient, the previously used and
seemingly different spin-fermion representations of the t-J model are shown to
be gauge related to each other. This new constraint can be treated in a
controlled way close to half-filling suggesting that the doped carrier
representation provides an appropriate theoretical framework to address the t-J
model in this region. This constraint also suggests that the t-J model can be
mapped onto a Kondo-Heisenberg lattice model. Such a mapping highlights
important physical similarities between the quasi two-dimensional heavy
fermions and the high-T superconductors. Finally we discuss the physical
implications of our model representation relating in particular the small
versus large Fermi surface crossover to the closure of the lattice spin gap.Comment: corrected and enlarged versio