Anionic Depolymerization Transition in ${\mathrm{IrTe}}_{2}$

Anionic Depolymerization Transition in ${IrTe}_{2}$

Yoon Seok Oh, J. J. Yang, Y. Horibe, and S.-W. Cheong

Phys. Rev. Lett. 110, 127209 – Published 22 March 2013

Abstract

Selenium substitution drastically increases the transition temperature of iridium ditelluride ( ${IrTe}_{2}$ ) to a diamagnetic superstructure from 278 to 560 K. Transmission electron microscopy experiments revealed that this enhancement is accompanied by the evolution of nonsinusoidal structure modulations from $q = 1 / 5 (10 \bar{1})$ to $q = 1 / 6 (10 \bar{1})$ types. These comprehensive results are consistent with the concept of the destabilization of polymeric Te-Te bonds at the transition, the temperature of which is increased by chemical and hydrostatic pressure and by the substitution of Te with the more electronegative Se. This temperature-induced depolymerization transition in ${IrTe}_{2}$ is unique in crystalline inorganic solids.

Received 15 October 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.127209

Authors & Affiliations

Yoon Seok Oh¹, J. J. Yang², Y. Horibe¹, and S.-W. Cheong^1,2

¹Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Piscataway, New Jersey 08854, USA
²Laboratory for Pohang Emergent Materials and Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea

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Vol. 110, Iss. 12 — 22 March 2013

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Figure 1
(a) Schematic perspective view of the polymeric network of Te-Te bonds. (b) Crystal structure of ${IrTe}_{2}$ showing Te-Te bond lengths and the relative sizes of the ${Ir}^{4 +}$ and ${Te}^{2 -}$ ions (the radii of the ${Ir}^{4 +}$ and ${Te}^{2 -}$ ions with 6 coordination sites are 0.62 and 2.2 Å, respectively). (c) Temperature dependence of the resistivity $ρ (T)$ of an ${IrTe}_{2}$ single crystal along the $c$ axis ( $ρ_{c}$ ) and in the $a b$ plane ( $ρ_{a b}$ ).Reuse & Permissions
Figure 2
Temperature dependence of (a) the magnetic susceptibility of polycrystalline ${IrTe}_{2 - x} {Se}_{x}$ in $μ_{0} H = 1 T$ upon warming, and (b) the resistivity of polycrystalline ${IrTe}_{2 - x} {Se}_{x}$ and a single crystal. $ρ (T)$ curves for $x \neq 0$ are shifted by arbitrary constants for clarity. (c) $ρ (T)$ of an ${IrTe}_{2}$ single crystal upon warming under various hydrostatic pressures. (d) Pressure dependence of the resistivity of an ${IrTe}_{2}$ single crystal at 300 K.Reuse & Permissions
Figure 3
(a)–(f) Electron diffraction patterns between the $\bar{1} 20$ and $02 \bar{1}$ fundamental spots for ${IrTe}_{2 - x} {Se}_{x}$ . The corresponding intensity profile of $x = 0.0$ is shown in the inset. Dark-field images of (g) $x = 0.0$ at $\sim 85 K$ and (h) $x = 0.45$ at room temperature (RT). High-resolution TEM images are shown in the upper right-hand insets of (g) and (h), displaying the superlattice modulations with periodicities of 1.4 and 1.7 nm associated with the $1 / 5 (10 \bar{1})$ and $1 / 6 (10 \bar{1})$ superlattice peaks, respectively, as well as antiphase boundaries (APB) due to phase shifts of the superlattice modulations. The lower left-hand inset of (h) displays a polarized optical microscope image of twin domains of $x = 0.45$ .Reuse & Permissions
Figure 4
(a) Temperature ( $T$ ) versus Se concentration ( $x$ ) phase diagram of ${IrTe}_{2 - x} {Se}_{x}$ constructed with $T_{C}$ values obtained from $ρ (T)$ measurements under warming (triangle) and cooling (inverted triangle). The diamond symbols indicate the $T_{C}$ values of ${IrTe}_{2 - x} {Se}_{x}$ single crystals ( $x = 0$ and 0.45). (b) Width of the thermal hysteresis ( $Δ T$ ) as a function of $x$ in ${IrTe}_{2 - x} {Se}_{x}$ . The vertical green guide line depicts the phase boundary between the $1 / 5 (10 \bar{1})$ and $1 / 6 (10 \bar{1})$ superstructures. Se-doping dependence of (c) the $a$ - and $c$ -axis lattice constants and (d) the $c / a$ ratio and the normalized volume determined from XRD results. The thin purple and thick green vertical lines indicate the phase boundaries of the paramagnetic to $1 / 5 (10 \bar{1})$ transition and the $1 / 5 (10 \bar{1})$ to $1 / 6 (10 \bar{1})$ transitions, respectively. (e) Hydrostatic pressure and calculated chemical pressure dependence of $T_{C}$ of ${IrTe}_{2}$ .Reuse & Permissions

Physical Review Letters

Anionic Depolymerization Transition in IrTe2

Yoon Seok Oh, J. J. Yang, Y. Horibe, and S.-W. Cheong

Phys. Rev. Lett. 110, 127209 – Published 22 March 2013

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Anionic Depolymerization Transition in ${IrTe}_{2}$