Doping Evolution of Energy Gaps in Bi₂Sr₂CaCu₂O_8+δ superconductors studied by Laser-based ARPES

The energy gap is a key quantity in understanding the high temperature superconductivity mechanism in cuprate superconductors. We have carried out comprehensive angle-resolved photoemission (ARPES) measurements on Bi₂Sr₂CaCu₂O_8+δ (Bi2212) superconductors by utilizing our high resolution laser-based ARPES system equipped with an angle-resolved time-of-flight (ARToF) electron energy analyzer and lasers with 7 and 11 eV photon energies. With high instrumental resolution (~1 meV) and wide coverage of the momentum space, we will report detailed doping, momentum and temperature dependences of the energy gap (superconducting gap and pseudogap) in Bi2212. Implications of these results will be discussed.