Novel electronic transition in layered IrTe$_{2}$

Layered chalcogenides such as 1T-TaS$_{2}$, 1T-TiSe$_{2}$, Bi$_{2}$Se$_{3}$, and MoS$_{2}$ exhibit rich low-dimensional physical properties such as superconductivity, topological insulator, charge density waves (CDW), and field-effect-transistor with high mobility. IrTe$_{2}$ forms in the layered CdI$_{2}$ structure, and exhibits diamagnetism and superlattice modulations below $\sim$260 K. In addition, superconductivity appears when the $\sim$260 K transition is fully suppressed by, for example, chemical doping. The origin of the $\sim$260 K transition in IrTe$_{2}$ has been controversial. It was claimed to be a structural transition, which suppresses electronic conduction. It was also reported that Fermi surface instability drives the transition - $i.e.$ it is charge density wave-type. In this talk, we present our comprehensive studies on electron diffraction and transport experiments under chemical/hydrostatic pressure to unveil the origin of the novel electronic transition in IrTe$_{2}$.