%0 Unpublished work
%T Temperature Dependent Zero-Field Splittings in Graphene
%+ Laboratoire Charles Coulomb (L2C)
%A Bray, C.
%A Maussang, K.
%A Consejo, C.
%A Delgado-Notario, J. A.
%A Krishtopenko, S. S.
%A Yahniuk, I.
%A Gebert, S.
%A Ruffenach, S.
%A Dinar, K.
%A Moench, E.
%A Indykiewicz, K.
%A Jouault, B.
%A Torres, J.
%A Meziani, Y. M.
%A Knap, W.
%A Yurgens, A.
%A Ganichev, S. D.
%A Teppe, F.
%Z Main text with figures (18 pages) and Supplementary Information (11 pages)
%8 2022-10-21
%D 2022
%Z 2209.14001
%Z Physics [physics]Preprints, Working Papers, ...
%X Graphene is a quantum spin Hall insulator with a 45 $\mu$eV 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.
%G English
%L hal-03824955
%U https://hal.science/hal-03824955
%~ CNRS
%~ L2C
%~ UNIV-MONTPELLIER
%~ ANR
%~ UM-2015-2021
%~ UM-EPE
%~ TEST3-HALCNRS