Signature of collective excitations close to the metal-to-insulator transition

Michal Karski

Institute of Theoretical Physics , University of Cologne, Zülpicher Str. 77, 50937 Cologne, Germany

A high-resolution calculation of the dynamical mean-field equations for the half-filled Hubbard model reveals a clear signature of collective excitations close to the metal-to-insulator transition. This calculation has become possible by current advances in dynamical density-matrix renormalization. The effect of collective excitations is seen as sharp peaks at the inner edges of the Hubbard bands. These peaks evidence a strong interaction between charge and collective degrees of freedom. The relevance of this finding to transition metal compounds is pointed out.