Enhancing charge-density-wave order in 1T-TiSe2 nanosheet by encapsulation with hexagonal Boron Nitride

TL;DR

This study demonstrates that encapsulating 1T-TiSe2 nanosheets with hexagonal Boron Nitride enhances charge density wave order, achieving higher transition temperatures and highlighting substrate choice as crucial for room temperature CDW applications.

Contribution

It reveals that h-BN encapsulation significantly enhances CDW order in 1T-TiSe2 nanosheets, enabling intrinsic CDW at higher temperatures and emphasizing substrate effects on 2D correlated electronic phases.

Findings

Encapsulation with h-BN increases CDW transition temperature up to 235 K.

Substrate disorder and phonons suppress CDW in ultrathin samples.

Proper substrate selection is key for room temperature CDW materials.

Abstract

Layered transition metal dichalcogenides (TMDs) provide an ideal platform for exploring the effects of dimensionality on correlated electronic phases such as charge density wave (CDW) order. When TMDs are reduced in thickness to the 2-D limit, it is expected that the substrates will exert considerable influence on the electron states. Here we report a study of the charge density wave (CDW) state in 1T-TiSe2 nanosheets of different thicknesses when the sheets are encapsulated by hexagonal Boron Nitride (h-BN) or supported on SiO2 substrate. Our results show that dimensionality reduction results in an enhancement of CDW order and that disorder and substrate phonons tends to destroy CDW order, preventing observation of intrinsic CDW transition in ultrathin samples. Encapsulated 10 nm thick 1T-TiSe2 samples exhibit intrinsic CDW with transition temperature as high as 235 K. Our study points out that choosing the right substrate is important in the search for room temperature CDW materials.