https://doi.org/10.1007/s100510050588
Photoemission, inverse photoemission and superconducting correlations in Hubbard and t-J ladders: role of the anisotropy between legs and rungs
1
Laboratoire de Physique Quantique (CNRS -UMR 5626) ,
Université Paul Sabatier, 31062 Toulouse, France
2
Instituto de Física Rosario, Consejo Nacional de
Investigaciones
Científicas y Técnicas y Departamento de Física,
Universidad Nacional de Rosario, Avenida Pellegrini 250, 2000-Rosario,
Argentina
3
Department of Physics and National High Magnetic Field Lab,
Florida State University,
Tallahassee, FL 32306, USA
Received:
22
April
1998
Revised:
23
July
1998
Accepted:
30
July
1998
Published online: 15 January 1999
Several experiments in the context of ladder materials have
recently shown that the
study of simple models of anisotropic ladders (i.e. with different couplings along legs and
rungs) is important for the understanding of these compounds. In this
paper Exact Diagonalization studies of the one-band Hubbard and t-J
models are reported for a variety of densities, couplings, and
anisotropy ratios. The emphasis is given to the one-particle spectral
function
which presents a flat quasiparticle dispersion at the chemical potential in some
region of parameter space. This is correlated with the existence of
strong pairing fluctuations, which themselves are correlated with
an enhancement of the bulk-extrapolated value for the two-hole
binding energy as well as with the strength of
the spin-gap in the hole-doped system.
Part of the results for the spectral function are explained using a
simple analytical picture valid when the hopping along the legs is small.
In particular, this picture predicts an insulating state at
quarter filling in agreement with the metal-insulator transition observed at
this special filling for increasing rung couplings.
The results are compared against previous literature, and in addition
pair-pair correlations using extended operators are also here reported.
PACS: 71.27.+a – Strongly correlated electron systems; heavy fermions / 74.72.-h – High-Tc compounds / 75.40.Mg – Numerical simulation studies / 79.60.-i – Photoemission and photoelectron spectra
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999