  The conduction band structure in methylammonium lead iodide (CH3NH3PbI3) was
studied both by angle-resolved two-photon photoemission spectroscopy (AR-2PPE)
with low-photon intensity and angle-resolved low-energy inverse photoelectron
spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along
the {\Gamma}M direction was observed by these independent methods under
different temperatures, and the dispersion was found to be consistent with band
calculations under the cubic phase. The effective mass of the electrons at the
{\Gamma} point was estimated to be (0.20+-0.05)m0 at 90 K. The observed energy
position was largely different between the AR-LEIPS and AR-2PPE, demonstrating
the electron correlation effects on the band structures. The present results
also indicate that the surface structure in CH3NH3PbI3 provides the
cubic-dominated electronic property even at lower temperatures.
