Density response of the t-J model and renormalization of breathing and half-breathing phonon modes: A slave-fermion calculation

• Published in: Physica. C, Superconductivity Vol. 341; pp. 117 - 120
• Main Authors: Horsch, P, Khaliullin, G, Oudovenko, V
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2000
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(00)00410-X

The density fluctuation spectrum N( k , ω) is calculated for the t- J model in the low-doping regime using a slave-fermion method for the constrained fermions. The obtained results for N( k , ω) are in good agreement with diagonalization results. The density response is characterized by incoherent, momentum dependent spectral functions reaching up to energies ∼ 8 t and a low-energy structure at energy ∼ J due to transitions in the quasiparticle band. N( k , ω) is shown to lead to a strong renormalization of planar bond-streching and breathing phonon modes with a large phonon linewidth at intermediate momenta caused by the low-energy response. Our results are consistent with recent neutron scattering data, showing the peculiar behavior of these modes.