Discovery of the Superconductivity in 3d Element Ni doped IrTe$_2$

TL;DR

This study reports the discovery of superconductivity in Ni-doped IrTe₂, where Ni substitution suppresses structural transitions and induces superconductivity around 2.6K, with anisotropic properties and weak paramagnetism.

Contribution

It demonstrates that Ni doping in IrTe₂ induces superconductivity and suppresses structural phase transitions, revealing a new pathway to tune properties in 3d element doped transition metal dichalcogenides.

Findings

Superconductivity observed at T_c ~ 2.6K in Ni-doped IrTe₂.

Ni doping suppresses the monoclinic phase, stabilizing the trigonal phase.

Weak paramagnetism with anisotropic superconducting properties observed.

Abstract

IrTe$_2$ with large spin-orbital coupling (SOC) shows a CDW-like first order structural phase transition from high-temperature trigonal phase to low-temperature monoclinic phase at 270 K, accompanying with a large jump in transport and magnetic measurement as well as in heat capacity. Here, the 3d element Ni has been doped into IrTe$_2$ by growing Ir$_{1-x}$Ni$_x$Te$_2$ single crystals. Both XRD and XPS results reveal that the Ni atoms have substituted for Ir, which is consistent with the calculation result. Like the CDW behaviour, the structural phase transition shows competition and coexistence with the superconductivity. The monoclinic phase transition has been suppressed gradually with the increase of the doping amount of Ni, at last giving rise to the stabilization of the trigonal phase with superconductivity. Within 0.1$\leq$x$\leq$0.2, Ir$_{1-x}$Ni$_x$Te$_2$ shows the superconductive behaviour with T$_c$ around 2.6K. The superconductivity shows anisotropy with dimensionless anisotropy parameter $\gamma$=$\xi_{//}$$/$$\xi_{\perp}$$\sim$ 2. Even Ni element shows ferromagnetic behaviour, Ir$_{1-x}$Ni$_x$Te$_2$ only shows weak paramagnetism, no ferromagnetic order is observed in it, which is coincident with the calculation result that their up and down spin density of states compensate each other well. In addition, for other 3d elements Fe, Co and Mn doped IrTe$_2$, only Ir$_{1-x}$Mn$_x$Te$_2$ owns magnetism with magnetic moment of 3.0$\mu$$_B$ to the supercell, theoretically.