New Lithium- and Diamine-Intercalated Superconductors Lix(CnH2n+4N2)yMoSe2 (n = 2, 6)

TL;DR

This paper reports the synthesis of new lithium- and diamine-intercalated MoSe2 superconductors, analyzing how electronic density of states and structural factors influence their superconducting properties.

Contribution

It introduces novel intercalation superconductors with specific intercalants and elucidates the relationship between electronic structure, interlayer spacing, and superconductivity in MoSe2-based materials.

Findings

Superconductivity observed at 4.2 K and 3.8-6.0 K in new intercalated compounds.

Superconductivity correlates with electronic density of states at the Fermi level.

Interlayer spacing influences superconductivity through electronic structure modifications.

Abstract

We have succeeded in synthesizing new intercalation superconductors Lix(C2H8N2)yMoSe2 and Lix(C6H16N2)yMoSe2 with Tc = 4.2 and 3.8-6.0 K, respectively, via the co-intercalation of lithium and ethylenediamine or hexamethylenediamine into semiconducting 2H-MoSe2. It has been found that the Tc values are related not to the interlayer spacing between MoSe2 layers so much but to the electronic density of states (EDOS) at the Fermi level. Moreover, only Li-intercalated LixMoSe2 with a small interlayer spacing has been found to be non-superconducting. Accordingly, it has been concluded that not only a sufficient amount of EDOS at the Fermi level due to the charge transfer from intercalated Li to MoSe2 layers but also the enhancement of the two-dimensionality of the crystal structure and/or electronic structure due to the expansion of the interlayer spacing between MoSe2 layers is necessary for the appearance of superconductivity in MoSe2-based intercalation superconductors. The pairing mechanism and the analogy to the superconductivity in the electric double-layer transistors of 2H-MoX2 (X = S, Se, Te) are discussed.