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Article Dans Une Revue Physical Review B Année : 2022

Temperature-dependent zero-field splittings in graphene

C. Bray
K. Maussang
J. Delgado-Notario
J. Eroms
  • Fonction : Auteur
B. Jouault

Résumé

Graphene is a quantum spin Hall insulator with a 45 µeV wide non-trivial topological gap induced by the intrinsic spin-orbit coupling. Even though this zero-field spin splitting is weak, it makes graphene an attractive candidate for applications in quantum technologies, given the resulting long spin relaxation time. On the other side, the staggered sub-lattice potential, resulting from the coupling of graphene with its boron nitride substrate, compensates intrinsic spin-orbit coupling and decreases the non-trivial topological gap, which may lead to the phase transition into trivial band insulator state. In this work, we present extensive experimental studies of the zero-field splittings in monolayer and bilayer graphene in a temperature range 2K-12K by means of sub-Terahertz photoconductivity-based electron spin resonance technique. Surprisingly, we observe a decrease of the spin splittings with increasing temperature. We discuss the origin of this phenomenon by considering possible physical mechanisms likely to induce a temperature dependence of the spin-orbit coupling. These include the difference in the expansion coefficients between the graphene and the boron nitride substrate or the metal contacts, the electron-phonon interactions, and the presence of a magnetic order at low temperature. Our experimental observation expands knowledge about the non-trivial topological gap in graphene.
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Dates et versions

hal-03925414 , version 1 (05-01-2023)

Identifiants

Citer

C. Bray, K. Maussang, C. Consejo, J. Delgado-Notario, S. Krishtopenko, et al.. Temperature-dependent zero-field splittings in graphene. Physical Review B, 2022, 106 (24), pp.245141. ⟨10.1103/PhysRevB.106.245141⟩. ⟨hal-03925414⟩
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