Suppression of charge density wave phases in ultrathin 1T-TaS2

TL;DR

This study investigates how reducing the thickness of 1T-TaS2 crystals affects their charge density wave phases, revealing suppression of certain phases below specific thicknesses due to weakened interlayer coupling.

Contribution

It provides experimental evidence on the thickness-dependent suppression of CDW phases in ultrathin 1T-TaS2 using temperature-dependent Raman spectroscopy.

Findings

Bulk-like CDW transition temperatures for crystals >10nm thick

Suppression of the commensurate CDW phase below 10nm

Diminished nearly commensurate CDW phase below 4nm

Abstract

Using temperature dependent Raman spectroscopy we address the question of how the transition from bulk to few atomic layers affects the charge density wave (CDW) phases in 1T-TaS2. We find that for crystals with thickness larger than approx 10nm the transition temperatures between the different phases as well as the hysteresis that occurs in the thermal cycle correspond to the ones expected for a bulk sample. However, when the crystals become thinner than $\approx 10nm$, the commensurate CDW phase is suppressed down to the experimentally accessible temperatures. In addition, the nearly commensurate CDW phase is diminished below approx 4nm. These findings suggest that the interlayer coupling plays a significant role in determining the properties of CDW systems consisting of a few unit cells in the vertical direction.