  We present a coupled cluster method (CCM) with optimized excitation
operators. The efficiency comes from a parameterized form of excitation
operators. The parameters are found by variational optimization procedure. The
resultant number of excitation operators is much smaller than that of the
conventional CCM theory. This property makes it possible to apply the method in
systems of solid state physics. Starting from Hartree-Fock state as the
reference state, i.e., the Fermi sea, we search for particle-hole excitation
operators such that the wave function of configuration interaction in terms of
these excitation operators spans a good approximation to the ground state. The
Match-pursuit algorithm is capable of doing the search of the excitation
operators. The resultant operators are our excitation operators for the CCM
wave function. We test the method by two dimensional fermionic Hubbard model on
a square lattice.
