Layered van der Waals topological metals of TaTMTe4 (TM = Ir, Rh, Ru) family

TL;DR

This study synthesizes and characterizes layered TaTMTe4 (TM=Ir, Rh, Ru) compounds, revealing metallic behavior, superconductivity in some variants, and evidence of Dirac cones, contributing to understanding their topological and electronic properties.

Contribution

It provides new synthesis, structural analysis, and electronic property insights into the TaTMTe4 family, highlighting the presence of Dirac cones and superconductivity.

Findings

TaIrTe4 and TaRhTe4 are metallic and diamagnetic.

Superconductivity observed below 4K in TaIr$_{1-x}$Rh$_x$Te$_4$ with high Rh content.

Linear magnetoresistance indicates Dirac cones near the Fermi level.

Abstract

Layered van~der~Waals materials of the family TaTMTe$_4$ (TM=Ir, Rh, Ru) are showing very interesting electronic properties. Here we report the synthesis, crystal growth and structural characterization of TaIrTe$_4$, TaRhTe$_4$, TaIr$_{1-x}$Rh$_{x}$Te$_4$ ($x = 0.06$; 0.14; 0.78; 0.92) and Ta$_{1+x}$Ru$_{1-x}$Te$_4$ single crystals. For Ta$_{1+x}$Ru$_{1-x}$Te$_4$ off-stoichiometry is shown. X-ray powder diffraction confirms that TaRhTe4 is isostructural to TaIrTe4. We show that all these compounds are metallic with diamagnetic behavior. Ta$_{1.26(2)}$Ru$_{0.75(2)}$Te$_{4.000(8)}$ exhibits an upturn in the resistivity at low temperatures which is strongly field dependent. Below $T \approx 4$K we observed signatures of the superconductivity in the TaIr$_{1-x}$Rh$_{x}$Te$_4$ compounds for $x = 0.92$. Magnetotransport measurements on all samples show weak magnetoresistance (MR) field dependence that is typically quadratic-in-field. However, for TaIr$_{1-x}$Rh$_{x}$Te$_4$ with $x\approx 0.78$, the MR has a linear term dominating in low fields that indicates the presence of Dirac cones in the vicinity of the Fermi energy. For TaRhTe$_4$ series the MR is almost isotropic. We have performed electronic structure calculations for isostructural TaIrTe$_4$ and TaRhTe$_4$ together with the projected total density of states. The main difference is appearance of the Rh-band close to the Fermi level.