NCTS (South)


DATE2014-03-13

TIME10:30

PLACER49223, Second Physics Building , NCKU

FIELDOther

SPEAKER Dr. Chi-Cheng Lee(李啟正) - School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST)

TITLEFirst-principles study on excitations: Quasiparticle, local excitation, and the exciton propagation

ABSTRACTKohn-Sham band structure within density functional theory has offered good interpretation of ARPES spectra. However, the original eigenstates no longer carry infinite quasiparticle lifetime upon the introduction of translational symmetry breakers, which require larger supercells in the calculations. To have a better representation of Kohn-Sham electrons, an unfolding method is presented to deliver the proper spectra weight in understanding the symmetry breaking that has been introduced to the original system. Beyond the one-particle excitation, I will discuss how the local two-particle excitations can be studied using real-space Wannier functions. From the Wannier function itself, rich information of form factor can be analyzed. Finally, a new kinetic kernel is introduced to further show how the local excitons can propagate in real-space and time, for example, the exciton dispersion. This new approach can also apply to study strongly correlated systems with strong local Coulomb interactions.