We 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 behavior, rather they are better characterized as a gapped continuum. As a consequence, the S shape becomes a kink, and superconductivity does not affect the dispersion as strongly. Finally, we note that optical phonons typically lead to a temperature-independent S shape, in disagreement with the observed dispersion.
|Original language||English (US)|
|Number of pages||12|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Nov 2004|
Bibliographical noteFunding Information:
We acknowledge useful discussions with Girsh Blumberg, Juan Carlos Campuzano, Erica Carlson, Dan Dessau, Hong Ding, Matthias Eschrig, Peter Johnson, Adam Kaminski, and Filip Ronning. A.C. is supported by the NSF-DMR 0240238 and M.N. by the U. S. Dept. of Energy, Office of Science, under Contract No. W-31-109-ENG-38. A.C. is thankful to Argonne National Laboratory for hospitality during the initial stages of this work.