Charge density wave and superconductivity modulated by c-axis stacking in the TaSe2 polytypes

TL;DR

This study explores how different c-axis stacking arrangements in TaSe2 polytypes influence their charge density wave and superconducting properties, revealing stacking as a key tuning parameter for correlated electronic states.

Contribution

It provides a detailed comparison of how stacking variations in TaSe2 polytypes modulate electronic phenomena like CDW and superconductivity, highlighting stacking as a crucial factor.

Findings

1T phase exhibits strong interlayer coupling and high-temperature CDW.

2H phase shows weak superconductivity and incommensurate CDW.

3R phase demonstrates enhanced superconductivity with modified interlayer hybridization.

Abstract

The layered transition metal dichalcogenide, TaSe2, exhibits rich electronic phenomena across its polymorphs, 1T, 2H, and 3R, largely driven by differences in atomic coordination and c-axis stacking. In the 1T phase, octahedral coordination and AA stacking promote strong interlayer coupling and stabilize a commensurate charge density wave (CDW) with star-of-David clusters that set in at high temperatures. The 2H phase exhibits trigonal prismatic coordination with AB stacking, and hosts both incommensurate and commensurate CDW phases and weak superconductivity at very low temperatures. The 3R phase, characterized by ABC stacking and trigonal prismatic coordination, exhibits enhanced superconductivity along with CDW order, attributed to modified interlayer hybridization and reduced CDW competition. These stacking-dependent variations in interlayer coupling are critical in tuning correlated states in the dichalcogenides.