Dispersion anomalies in cuprate superconductors

Andrey Chubukov

Department of Physics, University of Maryland, College Park, MD, 20742-4111, USA

I will argue that the shape of the dispersion along the nodal and antinodal directions in the cuprates can be understood as a consequence of the interaction of the electrons with collective spin excitations. In the normal state, the dispersion displays a crossover at an energy where the decay into spin fluctuations becomes relevant. In the superconducting state, the antinodal dispersion is strongly affected by the (π, π) spin resonance and displays an S-shape whose magnitude scales with the resonance intensity. For nodal fermions, relevant spin excitations do not have resonance. As a consequence, the $S-$shape becomes a kink, and superconductivity does not affect the dispersion as strongly.