https://doi.org/10.1140/epjb/e2003-00039-1
Possible phases of the two-dimensional t-t' Hubbard model
1
Institut für Theoretische Physik,
Universität Heidelberg, Philosophenweg 19, 69120 Heidelberg,
Germany
2
Department of Physics, Ternopil State Technical
University, 56 Rus'ka St., 46001 Ternopil, Ukraine
Corresponding author: a vaha@physique.usherb.ca
Received:
25
July
2002
Revised:
28
November
2002
Published online:
14
February
2003
We present a stability analysis of the 2D Hubbard model on a
square lattice for various values of the next-nearest-neighbor hopping
t' and electron concentration. Using
the free energy expression, derived by means of the flow equations
method, we have performed numerical calculation for the various
representations under the point group
in order to determine
at which temperature symmetry broken phases become more favorable
than the symmetric phase. A surprisingly large number of phases has
been observed. Some of them have an order parameter with many nodes in
-space. Commonly discussed types of order found by us are
antiferromagnetism,
-wave singlet superconductivity,
d-wave Pomeranchuk instability and flux phase. A few instabilities
newly observed are a triplet analog of the flux phase, a particle-hole
instability of p-type symmetry in the triplet channel which gives
rise to a phase of magnetic currents, an s*-magnetic phase, a
g-wave Pomeranchuk instability and the band splitting phase with
p-wave character. Other weaker instabilities are found
also. A comparison with experiments is made.
PACS: 71.10.Fd – Lattice fermion models (Hubbard model, etc.) / 71.27.+a – Strongly correlated electron systems; heavy fermions / 74.20.-z – Theories and models of superconducting state / 74.20.Rp – Pairing symmetries (other than s-wave)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003