Electronic properties across the first-order phase transition in Fe1.05Te

We present scanning tunneling microscopy and spectroscopic (STM/S) studies on Fe1.05Te single crystals. In this compound, the superconductivity appears upon Se doping and the physical properties are found to be extremely sensitive to non-stoichiometry and disorder. In our FeTe crystals, a first-order phase transition is observed around 57 K in the resistivity, magnetization, and the specific heat measurements. This transition is associated with a structural transition from a tetragonal P4/nmm to a monoclinic P21/m space group. At this temperature, the compound becomes antiferromagnetically ordered and the temperature dependence of the resistivity changes from log (-T) to T2. This observation suggests that the material behaves as a Fermi-liquid metal at low temperatures. Metallic behavior is also confirmed by the I-V characteristics of the STM measurements.