Doping evolution of kink from the contionously doped cuprate surface

We present the doping evolution of the kink dispersion at node by in-situ ARPES measuring on a continuously doped surface of Bi2212 using our recently pronounced surface treating technique of ozone/vacuum annealing [1]. We demonstrate the Fermi velocity (<5meV) decreases and the band velocity of middle energy (25~55 meV) is a constant when doping decreases. However, the band velocity beyond ~70 meV is larger and larger when goes to UD region. We propose a splendid scenario as a possibility to explain these exotic velocities of kink dispersion. We speculate there is an additional renormalisation to the Fermi velocity for the reason that the kink at ~ 10 meV comes from the coupling to boson modes like phonons. The band at middle energy constitutes by the “bared electron”, so its band velocity is independent with doping due to the rigid-band shift nature of Bi2212 [2]. However, for band dispersion higher than the ~70 meV, the electrons are fractionalized then they acquire a greater velocity. And this fractionalized effect becomes stronger when comes to more and more UD, so the band velocity becomes bigger and bigger.


Ref:
[1] Zhong, Y. G., et al., arXiv:1805.06450 (2018).
[2] Zhong, Y. G., et al., Sci. China-Phys. Mech. Astron. 61, 127403 (2018).