Spin-orbit coupling-enhanced valley ordering of malleable bands in twisted bilayer graphene on WSe2

Saisab Bhowmik, Bhaskar Ghawri, Youngju Park, Dongkyu Lee, Suvronil Datta, Radhika Soni, K. Watanabe, T. Taniguchi, Arindam Ghosh, Jeil Jung, U. Chandni

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Abstract

Recent experiments in magic-angle twisted bilayer graphene have revealed a wealth of novel electronic phases as a result of interaction-driven spin-valley flavour polarisation. In this work, we investigate correlated phases due to the combined effect of spin-orbit coupling-enhanced valley polarisation and the large density of states below half filling of the moiré band in twisted bilayer graphene coupled to tungsten diselenide. We observe an anomalous Hall effect, accompanied by a series of Lifshitz transitions that are highly tunable with carrier density and magnetic field. The magnetisation shows an abrupt change of sign near half-filling, confirming its orbital nature. While the Hall resistance is not quantised at zero magnetic fields—indicating a ground state with partial valley polarisation—perfect quantisation and complete valley polarisation are observed at finite fields. Our results illustrate that singularities in the flat bands in the presence of spin-orbit coupling can stabilise ordered phases even at non-integer moiré band fillings.

Original languageEnglish
Article number4055
JournalNature Communications
Volume14
Issue number1
DOIs
StatePublished - Dec 2023

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