Doping and momentum dependence of coupling strength in cuprate superconductors

ABSTRACT

Superconductivity is caused by the interaction between electrons by the exchange of bosonic excitations, however, this glue forming electron pairs is manifested itself by the coupling strength of the electrons to bosonic excitations. Here the doping and momentum dependence of the coupling strength of the electrons to spin excitations in cuprate superconductors is studied within the kinetic-energy-driven superconducting mechanism. The normal self-energy in the particle-hole channel and pairing self-energy in the particle-pariticle channel generated by the interaction between electrons by the exchange of spin excitation are employed to extract the coupling strengths of the electrons to spin excitations in the particle-hole and particle-particle channels, respectively. It is shown that below $T_{\mathrm{c}}$, both the coupling strengths in the particle-hole and particle-particle channels around the antinodes consist of two peaks, with a sharp low-energy peak located at 5 meV in the optimally doped regime, and a broad-band with a weak peak centred at 40 meV. In particular, this two-peak structure in the coupling strength in the particle-hole channel can persist into the normal-state, while the coupling strength in the particle-particle channel vanishes at the nodes. However, the positions of the peaks in the underdoped regime shift towards to higher energies with the increase of doping. More specifically, although the positions of the peaks move to lower energies from the antinode to the hot spot, the weights of the peaks decrease with the move of the momentum from the antinode to the hot spot, and fade away at the hot spots.

KEYWORDS:

• Coupling strength
• normal self-energy
• pairing self-energy
• cuprate superconductor

Acknowledgments

The authors would like to thank Professor Xingjiang Zhou and Dr. Deheng Gao for helpful discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China under Grant No. 2016YFA0300304, and the National Natural Science Foundation of China under Grant Nos. 11574032 and 11734002.