Charge-Orbital Density Wave and Superconductivity in the Strong Spin-Orbit Coupled ${\mathrm{IrTe}}_2:\mathrm{Pd}$

Using transmission electron microscopy, the anomalies in resistivity and magnetic susceptibility at $\sim 262\mathrm{K}$ in ${\mathrm{IrTe}}_2$ are found to accompany the superlattice peaks with $\stackrel{\rightharpoonup }{q}=(1/5,0,-1/5)$. The wave vector is consistent with our theoretical calculation for the Fermi surface nesting vector, indicating that the $\sim 262\mathrm{K}$ transition is of the charge-orbital density wave (DW) type. We also discovered that both Pd intercalation and substitution induce bulk superconductivity with $T_c$ up to $\sim 3\mathrm{K}$, which competes with DW in a quantum critical pointlike manner.

Figure 1

(a) Lattice structure of ${\mathrm{IrTe}}_2$. (b) Temperature-dependent magnetic susceptibility for ${\mathrm{Pd}}_x\mathrm{Ir}{\mathrm{Te}}_2$ ($0\le x\le 0.03$) in $H=2\mathrm{T}$. (c) Temperature-dependent resistivity for ${\mathrm{Pd}}_x{\mathrm{IrTe}}_2$ ($0\le x\le 0.04$) (normalized at 300 K). (d) Temperature-dependent magnetic susceptibility for ${\mathrm{Ir}}_{1-y}{\mathrm{Pd}}_y{\mathrm{Te}}_2$ ($0\le y\le 0.05$) in $H=2\mathrm{T}$. (e) Temperature-dependent resistivity for ${\mathrm{Ir}}_{1-y}{\mathrm{Pd}}_y{\mathrm{Te}}_2$ ($0\le y\le 0.07$) (normalized at 300 K). Black and light gray (red) arrows indicate the cooling and heating processes, respectively.

Figure 2

(a) Electron diffraction pattern of ${\mathrm{IrTe}}_2$ at 284 K. (b) Electron diffraction pattern of ${\mathrm{IrTe}}_2$ at 84 K. (c) Reciprocal lattice of ${\mathrm{IrTe}}_2$ at 84 K. Big balls represent the fundamental lattice, and small balls correspond to the superlattice. (d) The charge susceptibility $\chi (\stackrel{\rightharpoonup }{q})$ along $L^{\prime }(1/2,0,-1/2)\mathrm{\text{−}}\Gamma \mathrm{\text{−}}L(0,1/2,1/2)$. The dominating peak is at $\stackrel{\rightharpoonup }{q}=(\sim 1.1/5,0,\sim -1.1/5)$ (red arrow). Solid (black) circles are the data calculated without SO coupling, and open (blue) circles represent the data with SO coupling. (e) Inner and (f) outer Fermi surfaces of ${\mathrm{IrTe}}_2$.

Figure 3

(a) Temperature-dependent superconducting (SC) shielding [zero-field-cooled (ZFC)] and Meissner (FC) fraction data for ${\mathrm{Pd}}_x{\mathrm{IrTe}}_2$ ($0.02\le x\le 0.1$) in $H=10\mathrm{Oe}$. (b) Temperature-dependent resistivity for ${\mathrm{Pd}}_x{\mathrm{IrTe}}_2$ ($0.02\le x\le 0.1$) (normalized at 3.5 K). (c) Temperature-dependent SC fraction data for ${\mathrm{Ir}}_{1-y}{\mathrm{Pd}}_y{\mathrm{Te}}_2$ ($0.03\le y\le 0.07$) in $H=10\mathrm{Oe}$. (d) Temperature-dependent resistivity for ${\mathrm{Ir}}_{1-y}{\mathrm{Pd}}_y{\mathrm{Te}}_2$ ($0.03\le y\le 0.07$) (normalized at 3.5 K). (e) Magnetic hysteresis loop for ${\mathrm{Pd}}_{0.03}{\mathrm{IrTe}}_2$ at 2 K. (f) Magnetic hysteresis loop for ${\mathrm{Ir}}_{0.95}{\mathrm{Pd}}_{0.05}{\mathrm{Te}}_2$ at 1.8 K.

Figure 4

(a) Electronic phase diagram of ${\mathrm{Pd}}_x{\mathrm{IrTe}}_2$ (circles) and ${\mathrm{Ir}}_{1-y}{\mathrm{Pd}}_y{\mathrm{Te}}_2$ (diamonds). Dark gray (blue) symbols correspond to the DW transition temperatures, and light gray (red) symbols represent the superconducting transition temperatures. Open symbols indicate that the transition temperatures may be below our minimum available temperature.