Phase fluctuation in anti-ferromagnetic order and its effect on the pseudo-gap in electron doped cuprates

Chang-Young Kim, Yonsei University

Angle-resolved photoemission (ARPES) and infrared spectroscopy showed existence of pseudo gaps in electron doped cuprates. From the ARPES results, it was found that the locus of the pseudo-gap is where the original Fermi surface and (p,0)-(0,p) line cross each other in the momentum space. Since the (p,0)-(0,p) line is the anti-ferromagnetic (AF) Brillouin zone boundary, it has long been suspected that AF is the culprit for the pseudo-gap phenomena. However, some aspects of the experimental data cannot be explained by a simple model based on AF ordering, and the question of what causes the pseudo-gap in electron-doped materials has never been really answered.

In this presentation, we show our recent doping, temperature and rare earth element dependent ARPES results on electron doped cuprates. The results show that the pseudo-gap effect generally decreases as the doping and/or temperature increases, the pseudo-gap size is surprisingly intact. Instead of the gap size decreasing, the pseudo-gap rather is weakened through gap filling process.