Multi-layered chalcogenides with potential for magnetism and superconductivity

TL;DR

This study explores layered thallium copper chalcogenides, examining their potential for magnetism and superconductivity through synthesis, experimental measurements, and first-principles calculations, revealing a lack of magnetic or superconducting instability in these materials.

Contribution

The paper reports new Tl-based layered chalcogenides and combines experimental and theoretical analysis to assess their magnetic and superconducting potential, highlighting the absence of such properties.

Findings

No long-range magnetism observed in these materials.

First-principles calculations indicate a lack of Fermi-level spectral weight for magnetic or superconducting instability.

Layered structures with Fe show higher likelihood of magnetism.

Abstract

Layered thallium copper chalcogenides can form single, double, or triple layers of Cu-Ch separated by Tl sheets. Here we report on the preparation and properties of Tl-based materials of TlCu2Se2, TlCu4S3, TlCu4Se3 and TlCu6S4, and compare to reports on layered ACu2nChn+1 materials with A = Ba, K, Rb, and Cs, and Ch = S, Se. Having no long-range magnetism for these materials is quite surprising considering the possibilities of inter- and intra-layer exchange interactions through Cu 3d, and we measure by magnetic susceptibility and confirm by neutron diffraction. First principles density-functional theory calculations for both the single-layer TlCu2Se2 (isostructural to the 122 iron-based superconductors) and the double-layer TlCu4Se3 suggest a lack of Fermi-level spectral weight that is needed to drive a magnetic or superconducting instability. The electronic structure calculations show a much greater likelihood of magnetism for multiple structural layers with Fe.