STM studies of insulating cuprates and iron pnictides
Yayu
Wang
Department
of Physics,
Abstract. Although the mechanism of high Tc superconductivity in the cuprates
remains elusive, it is generally agreed that the key physics is that of doped
Mott insulators. In this talk we report
recent scanning tunneling microscopy (STM) studies of the atomic-scale
electronic structure of the cuprates near the Mott insulator limit. In the
parent compound the full electronic spectrum across the Mott–Hubbard gap
is uncovered, which reveals the particle–hole symmetric and spatially
uniform Hubbard bands. Defect-induced charge carriers are found to create broad
in-gap electronic states that are strongly localized in space. In the lightly
doped insulating regime, a V-shaped feature near the Fermi level emerges as a
result of spectral weight transfer mainly from the upper Hubbard band. It evolves smoothly into the pseudogap phase while
the high energy Mottness features remain. More recently, we found that in the
insulating iron pnictides the electronic structure shares striking similarities
to that of underdoped cuprates in the pseudogap regime. It suggests that the
doped Mott insulator scenario may also apply in the insulating regime of the
iron pnictide phase diagram, thus providing a new perspective for understanding
the iron-based superconductivity.
Host: Prof. W. Wu