Fig. 1: Structure and phase diagram of IrTe₂ nanoflakes.

a Schematic phase diagrams of TMDCs as a function of control parameter p, showing commensurate (C), incommensurate charge order (IC), and superconductivity (SC). Three different types of dome-shaped superconducting phase diagram, where the dome lies at the centre of a presumed quantum critical point (top), near the C-IC transition line (middle), or well inside the parent order (bottom). b Crystal structure of IrTe₂. c, d Schematic illustrations of the stripe order in IrTe₂ below T_s. The Ir-Ir dimerization (red) with a modulation vector q = (\(\frac{1}{5}\),0,\(\frac{1}{5}\)) is depicted (blue shade) on the triangular Ir layer (c) and across the stacked layers (d). The crystallographic axes for the high-T (a, b, and c) and the low-T (a^*, b^*, and c^*) structures are shown, together with the unit cell of the stripe phase (orange box). e Temperature dependence of the normalised resistivity ρ(T)/ρ(300 K) for IrTe₂ crystals with thickness (d) of 21, 56, and 90 nm. For clarity, ρ(T)/ρ(300 K) curves are offset vertically. Transition temperatures T_s,up and T_s,dn are determined (arrows) in opposite temperature sweeps. f Optical microscope image of a 56-nm-thick IrTe₂ crystal. g ρ(T)/ρ(3 K) curves for IrTe₂ crystals with d = 12–140 nm. h Phase diagram of IrTe₂ nanoflakes as a function of thickness d, obtained by transport (circle) and Raman spectroscopy (square) measurements. The transition temperatures T_s,up (red) and T_s,dn (blue) during warming and cooling are plotted with the superconducting transition temperature T_c (black), scaled by a factor of 10 for clarity. The error bars from the resistivity and Raman spectroscopy are defined by the width of the corresponding resistive transitions and the temperature step of 5 K between the measurements, respectively.