| pubmed-article:20867869 | pubmed:abstractText | Using low photon energy angle-resolved photoemission, we study the low-energy dispersion along the nodal (?,?) direction in Bi{2}Sr{2}CaCu{2}O{8+?} as a function of temperature. Less than 10 meV below the Fermi energy, the high-resolution data reveal a novel "kinklike" feature in the electron self-energy that is distinct from the larger well-known kink roughly 70 meV below E{F}. This new kink is strongest below the superconducting critical temperature and weakens substantially at higher temperatures. A corollary of this finding is that the Fermi velocity v{F}, as measured in this low-energy range, varies rapidly with temperature-increasing by almost 30% from 70 to 110 K. The behavior of v{F}(T) appears to shift as a function of doping, suggesting a departure from simple "universality" in the nodal Fermi velocity of cuprates. | lld:pubmed |
