UVSOR Lunch Seminar (2007-01)

Title: Charge-orbital ordered state in half-doped layered manganites

Speaker: Prof. Yunsang Lee
Affiliation: Department of Physics, Soongsil University, Korea

Date&Time: July 23, 14:00- (probably one hour)
Place: UVSOR Build. #304 (UVSOR seminar room)

Abstract:
One of the most attractive phenomena in doped Mott insulators is the
nano-scale self-organization and the associated complexity of
electronic systems due to the interplay among the charge, spin, and
orbital degrees of freedoms. In Mn-oxides near half-doping there
appears 'CE-type' magnetically ordered charge-orbital ordering (CO-OO),
where the zigzag chain-type of orbital arrangement and the related
ferromagnetic coupling might lead to the anisotropic electronic
response. We have investigated the in-plane optical anisotropy for the
CO-OO phase in half-doped layered manganites. Using optical
spectroscopy on a single domain sample with polarization dependence, we
found that the optical conductivity along the chain direction exhibits
smaller optical gap and lower energy distribution of the spectral
weight than that along the stripe (interchain) direction. Notably, for
a bilayer manganite the optical anisotropy is reversed in accord with
the rotation of orbital stripe with a variation of temperature. These
findings imply that the orbital stripe might work as a parameter of a
optical polarization-related device.