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Condensed Matter / Biophysics Seminar – Emanuel Tutuc, University of Texas at Austin

Date November 8 @ 4:00 pm - 5:00 pm

Twist-Controlled van der Waals Heterostructures

Heterostructures of atomic layers such as graphene, hexagonal boron-nitride, and transition metal dichalcogenides can serve as testbed for novel quantum phenomena in two-dimensions, and potential device applications. A key ingredient that has added a new dimension to the atomic layer heterostructures palette is the rotational control, and alignment of different two-dimensional (2D) layers.  We review here the experimental techniques that enable rotationally controlled heterostructures with accurate alignment of the individual layer crystal axes [1], and illustrate the applicability of this technique to rotationally aligned double layers of graphene separated by a tunnel barrier which display resonant, energy- and momentum-conserving tunneling in vertical transport, consistent with theoretical expectations [2].  When two 2D layers are overlaid with a relative twist, the resulting heterostructure shows a new type of periodicity associated with the moiré superlattice.  We discuss the transport and thermodynamic properties of twisted double bilayer graphene heterostructures, which reveal correlated insulators at fractional fillings of the moiré Brillouin zone, and the emergence of a time-reversal-invariant Chern insulator at charge neutrality in the presence of an applied transverse electric field [3].

[1] K. Kim et al., Nano Lett. 16, 1989 (2016); K. Kim et al., Proc. Natl. Acad. Sci. USA 114, 3364 (2017).

[2] G. W. Burg et al., Nano Lett. 17, 3919 (2017); G. W. Burg et al., Phys. Rev. Lett. 120, 177702 (2018).

[3] G. W. Burg et al., Phys. Rev. Lett. 123, 197702 (2019); Y. Wang et al., arXiv:2105.07104 (2021).

Host: Dominique Laroche

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Date:
November 8
Time:
4:00 pm - 5:00 pm
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