At ambient pressure, bulk 2H-NbS2 displays no charge density wave instability, which is at odds with the isostructural and isoelectronic compounds 2H-NbSe2, 2H-TaS2, and 2H-TaSe2, and in disagreement with harmonic calculations. Contradictory experimental results have been reported in supported single layers, as 1H-NbS2 on Au(111) does not display a charge density wave, whereas 1H-NbS2 on 6H-SiC(0001) endures a 3 x 3 reconstruction. Here, by carrying out quantum anharmonic calculations from first-principles, we evaluate the temperature dependence of phonon spectra in NbS2 bulk and single layer as a function of pressure/strain. For bulk 2H-NbS2, we find excellent agreement with inelastic X-ray spectra and demonstrate the removal of charge ordering due to anharmonicity. In the two-dimensional limit, we find an enhanced tendency toward charge density wave order. Freestanding 1H-NbS2 undergoes a 3 x 3 reconstruction, in agreement with data on 6H-SiC(0001) supported samples. Moreover, as strains smaller than 0.5% in the lattice parameter are enough to completely remove the 3 x 3 superstructure, deposition of 1H-NbS2 on flexible substrates or a small charge transfer via field-effect could lead to devices with dynamical switching on/off of charge order.

Quantum enhancement of charge density wave in NbS2 in the two-dimensional limit / Bianco, Raffaello; Errea, Ion; Monacelli, Lorenzo; Calandra, Matteo; Mauri, Francesco. - In: NANO LETTERS. - ISSN 1530-6984. - 19:5(2019), pp. 3098-3103. [10.1021/acs.nanolett.9b00504]

Quantum enhancement of charge density wave in NbS2 in the two-dimensional limit

Bianco, Raffaello;Monacelli, Lorenzo;Mauri, Francesco
2019

Abstract

At ambient pressure, bulk 2H-NbS2 displays no charge density wave instability, which is at odds with the isostructural and isoelectronic compounds 2H-NbSe2, 2H-TaS2, and 2H-TaSe2, and in disagreement with harmonic calculations. Contradictory experimental results have been reported in supported single layers, as 1H-NbS2 on Au(111) does not display a charge density wave, whereas 1H-NbS2 on 6H-SiC(0001) endures a 3 x 3 reconstruction. Here, by carrying out quantum anharmonic calculations from first-principles, we evaluate the temperature dependence of phonon spectra in NbS2 bulk and single layer as a function of pressure/strain. For bulk 2H-NbS2, we find excellent agreement with inelastic X-ray spectra and demonstrate the removal of charge ordering due to anharmonicity. In the two-dimensional limit, we find an enhanced tendency toward charge density wave order. Freestanding 1H-NbS2 undergoes a 3 x 3 reconstruction, in agreement with data on 6H-SiC(0001) supported samples. Moreover, as strains smaller than 0.5% in the lattice parameter are enough to completely remove the 3 x 3 superstructure, deposition of 1H-NbS2 on flexible substrates or a small charge transfer via field-effect could lead to devices with dynamical switching on/off of charge order.
2019
Physics; photon spectra; x-ray spectra
01 Pubblicazione su rivista::01a Articolo in rivista
Quantum enhancement of charge density wave in NbS2 in the two-dimensional limit / Bianco, Raffaello; Errea, Ion; Monacelli, Lorenzo; Calandra, Matteo; Mauri, Francesco. - In: NANO LETTERS. - ISSN 1530-6984. - 19:5(2019), pp. 3098-3103. [10.1021/acs.nanolett.9b00504]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1277475
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