  The Hall effect is investigated in detail for nonsuperconducting and
superconducting FeTe thin films. The Hall coefficient commonly exhibits a sign
reversal from positive in a high-temperature paramagnetic state to negative in
a low-temperature antiferromagnetic state. Phenomenological analysis by a
simple two-band Drude model indicates that hole mobility is significantly
suppressed in the antiferromagnetic state. When suppression of the hole
mobility is insufficient, superconductivity shows up in FeTe. This result
strongly suggests that the itinerancy in both hole and electron channels is the
essential factor for the occurrence of superconductivity in iron chalcogenide
superconductors.
