Novel phase transitions in iridium dichalcogenides

5d transition metal oxides has attracted lots of attention because of exotic electronic phase resulted from entanglement of strong spin-orbit coupling and electron correlation in 5d orbital. In this manner, 5d transition metal chalcogenides is another intriguing 5d compound to have a rich variety of strongly correlated electronic states. In fact, recent studies of IrTe$_{2}$ reported chemical-doping/intercalation (Pd, Pt, Cu, and Rh) induced superconductivity and the unconventional structural modulations below $\sim$260 K. The simple empirical features of IrTe$_{2}$ resemble the conventional charge density waves (CDW) in the 3d/4d layered chalcogenides (e.g. 1T-TaS$_{2}$, and 1T-TiSe$_{2}$, etc.). But, recent corroborative experimental results indicate that instability of covalency of Ir ions induces the structural phase transition associated with soliton lattice of Te-Te covalent bonding. So far, there exist controversy to identify the exotic phase transition of IrTe$_{2}$. In this talk, we introduce recent investigations and discuss the phase transition in IrTe$_{2}$.