  We report encapsulated C60 molecules on electron transport in carbon-nanotube
peapod quantum dots. We find atomic-like behaviors with doubly degenerate
electronic levels, which exist only around ground states, by single electron
spectroscopy measured at low back-gate voltages (Vbg's). Correlation with
presence of nearly free electrons (NFEs) unique to the peapods is discussed. In
contrast, we find that encapsulated C60 molecules do not affect to single
charging effect. Moreover, we find anomalously high values of powers observed
in power laws in conductance versus energy relationships, which are strongly
associated with the doubly degenerate levels. It is revealed that the powers
originate from Tomonaga-Luttinger liquids via the occupied doubly degenerate
levels. Encapsulated C60 molecules do not eliminate a ballistic charge
transport in single-walled nanotubes.
