Disentangling orbital and valley Hall effects in bilayers of transition metal dichalcogenides
Cysne, Tarik P. (Universidade Federal Fluminense. Instituto de Física)
Costa, Marcio (Universidade Federal Fluminense. Instituto de Física)
Canonico, Luis M. (Institut Català de Nanociència i Nanotecnologia)
Nardelli, M. Buongiorno (University of North Texas. Department of Physics)
Muniz, R. B. (Universidade Federal Fluminense. Instituto de Física)
Rappoport, Tatiana Gabriela (Universidade Federal do Rio de Janeiro. Instituto de Física)

Data:	2021
Resum:	It has been recently shown that monolayers of transition metal dichalcogenides (TMDs) in the 2H structural phase exhibit relatively large orbital Hall conductivity plateaus within their energy band gaps, where their spin Hall conductivities vanish [Canonico et al. , Phys. Rev. B 101, 161409 (2020)PRBMDO2469-995010. 1103/PhysRevB. 101. 161409; Bhowal and Satpathy, Phys. Rev. B 102, 035409 (2020)PRBMDO2469-995010. 1103/PhysRevB. 102. 035409]. However, since the valley Hall effect (VHE) in these systems also generates a transverse flow of orbital angular momentum, it becomes experimentally challenging to distinguish between the two effects in these materials. The VHE requires inversion symmetry breaking to occur, which takes place in the TMD monolayers but not in the bilayers. We show that a bilayer of 2H-MoS2 is an orbital Hall insulator that exhibits a sizeable orbital Hall effect in the absence of both spin and valley Hall effects. This phase can be characterized by an orbital Chern number that assumes the value CL=2 for the 2H-MoS2 bilayer and CL=1 for the monolayer, confirming the topological nature of these orbital-Hall insulator systems. Our results are based on density functional theory and low-energy effective model calculations and strongly suggest that bilayers of TMDs are highly suitable platforms for direct observation of the orbital Hall insulating phase in two-dimensional materials. Implications of our findings for attempts to observe the VHE in TMD bilayers are also discussed.
Ajuts:	Agencia Estatal de Investigación PCI2018-093120 Ministerio de Economía y Competitividad SEV-2017-0706
Nota:	Altres ajuts: ICN2 is funded by the CERCA Programme/Generalitat de Catalunya.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió sotmesa a revisió
Matèria:	Direct observations ; Hall conductivity ; Inversion symmetry ; Model calculations ; Orbital angular momentum ; Spin hall conductivity ; Transition metal dichalcogenides ; Two-dimensional materials
Publicat a:	Physical review letters, Vol. 126, issue 5 (Feb. 2021) , art. 56601, ISSN 1079-7114

DOI: 10.1103/PhysRevLett.126.056601

Preprint 12 p, 11.9 MB

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