A Gapped Phase in Semimetallic Td -WTe2 Induced by Lithium Intercalation

Mengjing Wang; Aakash Kumar; Hao Dong; John M Woods; Joshua V Pondick; Shiyu Xu; David J Hynek; Peijun Guo; Diana Y Qiu; Judy J Cha

doi:10.1002/adma.202200861

A Gapped Phase in Semimetallic T_d -WTe₂ Induced by Lithium Intercalation

Adv Mater. 2022 Jun;34(24):e2200861. doi: 10.1002/adma.202200861. Epub 2022 May 12.

Authors

Mengjing Wang^{1

2}, Aakash Kumar^{1

2}, Hao Dong^{2

3}, John M Woods^{1

2}, Joshua V Pondick^{1

2}, Shiyu Xu^{1

2}, David J Hynek^{1

2}, Peijun Guo^{2

3}, Diana Y Qiu^{1

2}, Judy J Cha^{1

2}

Affiliations

¹ Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA.
² Energy Sciences Institute, Yale West Campus, West Haven, CT, 06516, USA.
³ Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, 06511, USA.

PMID: 35488783
DOI: 10.1002/adma.202200861

Abstract

The Weyl semimetal WTe₂ has shown several correlated electronic behaviors, such as the quantum spin Hall effect, superconductivity, ferroelectricity, and a possible exciton insulator state, all of which can be tuned by various physical and chemical approaches. Here, a new electronic phase in WTe₂ induced by lithium intercalation is discovered. The new phase exhibits an increasing resistivity with decreasing temperature and its carrier density is almost two orders of magnitude lower than the carrier density of the semimetallic T_d phase, probed by in situ Hall measurements as a function of lithium intercalation. The theoretical calculations predict the new lithiated phase to be a potential charge density wave (CDW) phase with a bandgap of ≈0.14 eV, in good agreement with the in situ transport data. The new phase is structurally distinct from the initial T_d phase, characterized by polarization-angle-dependent Raman spectroscopy, and large lattice distortions close to 6% are predicted in the new phase. This finding of a new gapped phase in a 2D semimetal demonstrates electrochemical intercalation as a powerful tuning knob for modulating electron density and phase stability in 2D materials.

Keywords: charge density waves; electron doping; lithium intercalation; phase transitions; tungsten ditelluride.