20-021 Strain-induced stripe phase in charge-ordered single layer NbSe_2

Fabrizio Cossu, Krisztián Palotás, Sagar Sarkar, Igor Di Marco, Alireza Akbari

NPG Asia Materials 12, 24 (2020)

https://doi.org/10.1038/s41427-020-0207-x

Abstract

Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe_2, a triangular 3 × 3 structural modulation is coupled to a charge modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a 4 × 4 modulation. We employ ab initio calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe_2, relating the stripe phase to compressive isotropic strain, favouring the 4 × 4 modulation. The observed wavelength of the charge modulation is also reproduced with a good accuracy.

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