Why the anti-nodal quasiparticle dispersion is so flat in the superconducting cuprates?

Abstract

The emergence of the coherent quasiparticle peak and the development of the peak-dip-hump structure in the anti-nodal region below $T_c$ is the most prominent non-BCS signature of the underdoped high-$T_c$ cuprates, in which no coherent quasiparticle can be defined in the anti-nodal region above $T_c$. The peak-dip-hump structure has been commonly interpreted as the result of the coupling of the electron to some Bosonic mode. However, such an electron-Boson coupling picture does not answer the question of \textit{why the quasiparticle dispersion is so flat in the anti-nodal region}, a behavior totally unexpected for Bogoliubov quasiparticle in a d-wave BCS superconductor. Here we show that the sharp quasiparticle peak in the anti-nodal region should be understood as a new pole in the electron Green's function generated by the strong coupling of the electron to diffusive spin fluctuation around the antiferromagnetic wave vector $\mathbf{Q}=(\pi ,\pi )$, rather than a nearly free Bogoliubov quasiparticle in a d-wave BCS superconductor. More specifically, we find that the normal self-energy of the electron from the scattering with the diffusive spin fluctuation manifests itself mainly as a level repulsion effect and is responsible for the reduction of both the quasiparticle dispersion and the quasiparticle dissipation rate in the anti-nodal region. We argue that the peak-dip separation in the anti-nodal spectrum should not be interpreted as the energy of the pairing glue.

6 pages, 5 figures, corrected some misleading statements in the first version

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Cited by in corpus (1)

• A short review of the recent progresses in the study of the cuprate superconductivity