Coexistence of elastic modulations in the charge density wave state of 2H-NbSe₂

Bulk and single-layer 2H-NbSe₂ exhibit identical charge density wave order (CDW) with a quasi-commensurate 3 × 3 superlattice periodicity. Here we combine scanning tunnelling microscopy (STM) imaging at T = 1 K of 2H-NbSe₂ with first-principles density functional theory (DFT) calculations to investi...

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Detalles Bibliográficos
Autores: Guster, Bogdan|||0000-0003-1305-1862, Rubio Verdú, Carmen|||0000-0002-6103-7734, Robles, Roberto|||0000-0001-7808-0395, Zaldívar, Javier, Dreher, Paul, Pruneda, Miguel|||0000-0002-3621-6095, Silva-Guillén, Jose Angel|||0000-0002-0483-5334, Choi, Deung-Jang, Pascual, José I.|||0000-0002-7152-4747, Ugeda, Miguel M., Ordejon, Pablo|||0000-0002-2353-2793, Canadell Casanova, Enric|||0000-0002-4663-5226
Tipo de recurso: artículo
Fecha de publicación:2019
País:España
Institución:Universitat Autònoma de Barcelona
Repositorio:Dipòsit Digital de Documents de la UAB
Idioma:inglés
OAI Identifier:oai:ddd.uab.cat:215015
Acceso en línea:https://ddd.uab.cat/record/215015
https://dx.doi.org/urn:doi:10.1021/acs.nanolett.9b00268
Access Level:acceso abierto
Palabra clave:Charge density waves
Transition metal dichalcogenides
DFT calculations
2H-NbSe₂
STM
Descripción
Sumario:Bulk and single-layer 2H-NbSe₂ exhibit identical charge density wave order (CDW) with a quasi-commensurate 3 × 3 superlattice periodicity. Here we combine scanning tunnelling microscopy (STM) imaging at T = 1 K of 2H-NbSe₂ with first-principles density functional theory (DFT) calculations to investigate the structural atomic rearrangement of this CDW phase. Our calculations for single-layers reveal that six different atomic structures are compatible with the 3 × 3 CDW distortion, although all of them lie on a very narrow energy range of at most 3 meV per formula unit, suggesting the coexistence of such structures. Our atomically resolved STM images of bulk 2H-NbSe₂ unambiguously confirm this by identifying two of these structures. Remarkably, these structures differ from the X-ray crystal structure reported for the bulk 3 × 3 CDW which in fact is also one of the six DFT structures located for the single-layer. Our calculations also show that due to the minute energy difference between the different phases, the ground state of the 3 × 3 CDW could be extremely sensitive to doping, external strain or internal pressure within the crystal. The presence of multiphase CDW order in 2H-NbSe₂ may provide further understanding of its low temperature state and the competition between different instabilities.

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