84 research outputs found
Magnon-mediated interactions between fermions depend strongly on the lattice structure
We propose two new methods to calculate exactly the spectrum of two
spin- charge carriers moving in a ferromagnetic background, at zero
temperature. We find that if the spins are located on a different sublattice
than that on which the fermions move, magnon-mediated effective interactions
are very strong and can bind the fermions into low-energy bipolarons with
triplet character. This never happens in models where spins and charge carriers
share the same lattice, whether they are in the same band or in different
bands. This proves that effective one-lattice models do not describe correctly
the low-energy part of the two-carrier spectrum of a two-sublattice model, even
though they may describe the low-energy single-carrier spectrum appropriately
High-spin polaron in lightly doped CuO planes
We device and investigate numerically a minimal yet detailed spin polaron
model that describes lightly doped CuO layers. The low-energy physics of a
hole is studied by total-spin-resolved exact diagonalization on clusters of up
to 32 CuO unit cells, revealing features missed by previous studies. In
particular, spin-polaron states with total spin 3/2 are the lowest eigenstates
in several regions of the Brillouin zone. In these regions, and also at other
points the quasiparticle weight is identically zero, indicating orthogonal
states to those represented in the one electron Green's function. This
highlights the importance of proper treatment of spin fluctuations in the
many-body background.Comment: To appear in Phys. Rev. Lett. Final version and Supplementary
Materials will be available at the journal's websit
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