Kohn-Luttinger instability of the Hubbard model in two dimensions: Variational approach

J Mráz, R Hlubina - Physical Review B, 2003 - APS
J Mráz, R Hlubina
Physical Review B, 2003APS
An effective Hamiltonian for the Kohn-Luttinger superconductor is constructed and solved in
the BCS approximation. The method is applied to the t− t′ Hubbard model in two
dimensions with the following results:(i) The superconducting phase diagram at half filling is
shown to provide a weak-coupling analog of the recently proposed spin liquid state in the J
1− J 2 Heisenberg model.(ii) In the parameter region relevant for the cuprates, we have
found a nontrivial energy dependence of the gap function in the dominant d-wave pairing …
Abstract
An effective Hamiltonian for the Kohn-Luttinger superconductor is constructed and solved in the BCS approximation. The method is applied to the t− t′ Hubbard model in two dimensions with the following results:(i) The superconducting phase diagram at half filling is shown to provide a weak-coupling analog of the recently proposed spin liquid state in the J 1− J 2 Heisenberg model.(ii) In the parameter region relevant for the cuprates, we have found a nontrivial energy dependence of the gap function in the dominant d-wave pairing sector. The hot spot effect in the angular dependence of the superconducting gap is shown to be quite weak.
American Physical Society
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