Weak localization as a probe of spin-orbit-induced spin-split bands in bilayer graphene proximity coupled to WSe 2

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Proximity coupling of bilayer graphene (BLG) to transition metal dichalcogenides (TMDs) offers a promising route to engineer gate-tunable spin-orbit coupling (SOC) while preserving BLG’s exceptional electronic properties. This tunability arises from the layer-asymmetric electronic structure of gapped BLG, where SOC acts predominantly on the layer in contact with the TMD. Here, we present a high-quality <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mrow> <a:mi>BLG</a:mi> <a:mo>/</a:mo> </a:mrow> </a:mrow> <a:mrow> <a:msub> <a:mi>WSe</a:mi> <a:mn>2</a:mn> </a:msub> </a:mrow> </a:math> device with a proximity-induced SOC gap and excellent electrostatic control. Operating in a quasiballistic regime, our double-gated heterostructure allows a gate-defined <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>p</c:mi> </c:math> - <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>n</e:mi> </e:math> - <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>p</g:mi> </g:math> cavity to be formed and clear weak antilocalization (WAL) features to be shown consistent with Rashba-type SOC. At lower hole densities, a transition to a pronounced weak-localization (WL) feature is observed, signaling transport through a single spin-split valence band. These findings–in agreement with calculations–provide direct spectroscopic evidence of a proximity-induced spin-split band in BLG and underscore the potential of BLG/TMD heterostructures for spintronics and spin-based quantum technologies.