Two-mode variational Monte Carlo study of quasiparticle excitations in cuprate superconductors

Recent measurements of quasiparticles in hole-doped cuprates revealed highly unusual features: (i) the doping-independent Fermi velocity, (ii) two energy scales in the quasiparticle spectral function, and (iii) a suppression of the low-energy spectral weight near the zone center. We explain these important facts by a novel two-mode variational Monte Carlo (VMC) study of the t-J model, which resolves a long-standing issue of the sum rule for quasiparticle spectral weights in VMC studies. The electron-doped case is also discussed.