Titanium ditelluride: Band structure, photoemission, and electrical and magnetic properties

We present a study of angle-resolved photoemission of the layered compound Ti${\mathrm{Te}}_2$. The results are compared to augmented-plane-wave band-structure calculations which predict Ti${\mathrm{Te}}_2$ to be a semimetal with an overlap of valence and conduction bands of 0.6 eV. Reasonable agreement with the calculations is found except for an almost dispersionless band found just below the Fermi level which is not present in the theory. This band is argued to result from either a narrow impurity band or localization of electrons due to the formation of polarons. From an analysis of resistivity, thermoelectric power, and Hall effect, we deduced the carrier concentrations and mobilities for ${\mathrm{Ti}}_{1.01}$ ${\mathrm{Te}}_2$. The large value of the Pauli susceptibility indicates large exchange enhancement. At 150 K, a phase transition was detected in magnetic susceptibility measurements. The corresponding lattice distortion could not be observed directly.