Graphene’s minimal intrinsic spin-orbit coupling makes it an ideal host for proximity-induced effects from adjacent transition metal dichalcogenides such as WSe\u2082. By placing graphene in contact with WSe\u2082, we can engineer strong spin-orbit interaction and break inversion symmetry in a fully gate-tunable device, realising topological phases and novel transport effects that are absent in pristine graphene.<\/p>\n\n\n\n
Some representative results are mentioned below: <\/p>\n\n\n\n
ABA-stacked trilayer graphene has a band structure comprising a monolayer-like linear band and a bilayer-like quadratic band, giving rise to a richer phase diagram than either mono- or bilayer graphene. By applying large electric displacement fields, we break the layer symmetry and drive the system through a series of symmetry-breaking transitions into gully-polarised and layer-polarised states. These phases have no bilayer analogue and arise from the unique multi-band structure of trilayer graphene. Our results establish ABA trilayer graphene as a new platform for studying interaction-driven symmetry breaking tunable by electric field.<\/p>\n\n\n\n
S. Kaur, U. Ghorai, A. Samanta, K. Watanabe, T. Taniguchi, R. Sensarma, Aveek Bid \u2014 Phys. Rev. B 112, L161103 (2025)<\/a> | arXiv:2503.21314<\/a><\/p>\n\n\n\n Band inversion \u2014 where the ordering of conduction and valence bands is reversed relative to the atomic limit \u2014 is the defining feature of topological insulators and semimetals. We demonstrate gate-controlled band inversion in ABA trilayer graphene, where an applied displacement field continuously tunes the system through a topological transition in the bulk band structure. The ability to switch between topologically trivial and non-trivial band structures using a single gate voltage in an all-carbon device opens a route to electrostatically reconfigurable topological devices.<\/p>\n\n\n\n H. K. Mann, S. Kaur, S. Mullick, P. Tiwari, K. Watanabe, T. Taniguchi, Aveek Bid \u2014 Phys. Rev. B 111, 235118 (2025)<\/a> | arXiv:2502.15232<\/a><\/p>\n\n\n\n We report a large antisymmetric (odd-parity) magnetoresistance in bilayer graphene brought into proximity with a magnetic insulator. The magnetoresistance is observed at room temperature and can be tuned over orders of magnitude using a gate voltage \u2014 making it one of the largest electrically controllable magnetoresistance effects reported in a 2D material. Combined experimental and theoretical analysis identifies this as a nonlinear Hall-family effect arising from the broken time-reversal and inversion symmetry of the magnetised bilayer graphene band structure. The room-temperature operation and electrical tunability make this system attractive for magnetic sensing and spintronics applications.<\/p>\n\n\n\n D. Sahani, S. Das, K. Watanabe, T. Taniguchi, A. Agarwal, Aveek Bid \u2014 Phys. Rev. Lett. 134, 106301 (2025)<\/a> | arXiv:2407.14071<\/a><\/p>\n\n\n\n We provide experimental evidence of a time-reversal symmetric Hall effect in high-mobility graphene\u2013WSe\u2082 heterostructures. This linear, dissipative Hall effect persists up to room temperature and can be tuned in both magnitude and sign by an external perpendicular electric field. Our joint experimental and theoretical study establishes that strain-induced band anisotropy in graphene, combined with broken inversion symmetry from WSe\u2082, produces this unconventional Hall response. Graphene\u2013TMD heterostructures are thereby established as an excellent platform for studying transport effects arising from broken symmetries in band-engineered two-dimensional systems.<\/p>\n\n\n\n P. Tiwari, D. Sahani, A. Chakraborty, K. Das, K. Watanabe, T. Taniguchi, A. Agarwal, Aveek Bid \u2014 Nano Lett. 23, 6792 (2023)<\/a> | arXiv:2301.01912<\/a><\/p>\n\n\n\n The quantum spin Hall (QSH) insulator is a topological phase characterised by helical edge modes protected by time-reversal symmetry. Although graphene was the material in which QSH was first theoretically predicted, observation of this phase in graphene had remained elusive due to its weak intrinsic spin-orbit coupling. We observed QSH in bilayer graphene by inducing strong spin-orbit coupling through proximity with single-layer WSe\u2082. Multiple complementary measurements \u2014 quantised conductance, weak antilocalization, asymmetric band gap, and large spin Hall signal \u2014 all confirm the realisation of the QSH phase in a fully gate-tunable van der Waals heterostructure.<\/p>\n\n\n\n P. Tiwari, S. K. Srivastav, S. Ray, T. Das, Aveek Bid \u2014 ACS Nano 15, 916 (2021)<\/a> | arXiv:2003.10292<\/a><\/p>\n\n\n\n We report an electric-field-induced transition from a topologically trivial to a topologically non-trivial band structure in a bilayer graphene\/WSe\u2082 heterostructure. The low-energy carriers experience an effective valley Zeeman spin-orbit interaction that can be switched on or off by a transverse displacement field, or transferred between valence and conduction bands \u2014 realising the theoretically predicted spin-orbit valve effect. A gate-tunable transition from weak localisation to weak antilocalization at constant carrier density provides direct evidence for the SOI-induced band splitting at the K and K\u2032 valleys, with implications for electrically controlled spin transport in two-dimensional materials.<\/p>\n\n\n\n P. Tiwari, S. K. Srivastav, Aveek Bid \u2014 Phys. Rev. Lett. 126, 096801 (2021)<\/a> | arXiv:2103.06529<\/a><\/p>\n\n\n\n Proximity-induced spin-orbit coupling in graphene has driven observations of topological phases and spin-filtering effects, but a quantitative picture of the resulting band structure was missing. We report the experimental determination of the band structure of single-layer graphene in the presence of strong proximity-induced spin-orbit coupling from WSe\u2082, through measurements of quantum oscillations in high-mobility hBN-encapsulated devices. We observe clear spin-splitting of the graphene bands and establish that the low-energy dispersion is dominated by valley-Zeeman and Rashba spin-orbit coupling, with evidence for band-gap opening and band inversion in the graphene.<\/p>\n\n\n\n P. Tiwari, M. K. Jat, A. Udupa, D. S. Narang, K. Watanabe, T. Taniguchi, D. Sen, Aveek Bid \u2014 npj 2D Mater. Appl. 6, 68 (2022)<\/a> | arXiv:2210.08926<\/a><\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Graphene’s minimal intrinsic spin-orbit coupling makes it an ideal host for proximity-induced effects from adjacent transition metal dichalcogenides such as WSe\u2082. By placing graphene in contact with WSe\u2082, we can engineer strong spin-orbit interaction and break inversion symmetry in a fully gate-tunable device, realising topological phases and novel transport effects that are absent in pristine […]<\/p>\n","protected":false},"author":4,"featured_media":4245,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[41],"tags":[],"class_list":["post-4941","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/posts\/4941","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/comments?post=4941"}],"version-history":[{"count":2,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/posts\/4941\/revisions"}],"predecessor-version":[{"id":4950,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/posts\/4941\/revisions\/4950"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/media\/4245"}],"wp:attachment":[{"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/media?parent=4941"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/categories?post=4941"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/physics.iisc.ac.in\/~aveek_bid\/wp-json\/wp\/v2\/tags?post=4941"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n\n\n\nTunable band inversion in ABA trilayer graphene Phys. Rev. B (2025)<\/a><\/h3>\n\n\n\n
\n\n\n\nGiant gate-controlled room-temperature odd-parity magnetoresistance in magnetised bilayer graphene Phys. Rev. Lett. (2025)<\/a><\/h3>\n\n\n\n
\n\n\n\nObservation of the time-reversal symmetric Hall effect in graphene\u2013WSe\u2082 heterostructures at room temperature Nano Letters (2023)<\/a><\/h3>\n\n\n\n
\n\n\n\nTime-reversal invariant helical edge-modes in bilayer graphene\/WSe\u2082 heterostructure ACS Nano (2021)<\/a><\/h3>\n\n\n\n
\n\n\n\nElectric-field-tunable valley Zeeman effect in bilayer graphene heterostructures: realization of the spin-orbit valve effect Phys. Rev. Lett. (2021)<\/a><\/h3>\n\n\n\n
\n\n\n\nExperimental observation of spin-split energy dispersion in high-mobility single-layer graphene\/WSe\u2082 heterostructures npj 2D Materials and Applications (2022)<\/a><\/h3>\n\n\n\n