1:45 pm GCIS W301/303
Moire Materials.
Recent progress in fabricating two-dimensional material devices hascreated an opportunity to study the properties of quantum metamaterials inwhich electrons exhibit strongly-correlated and topologically non-trivialproperties that are rare in naturally occuring crystals. For example,two-dimensional van der Waals crystals that are overlaid with a difference inlattice constant or a relative twist form a moiré pattern. In semiconductors and semimetals, the low-energyelectronic properties of these systems are accurately described by Hamiltoniansthat have the periodicity of the moiré pattern – artificial crystals withlattice constants on the 10 nm scale. Since the miniband widths in both graphene and TMD moiré materials canbe made small compared to interaction energy scales (by mechanisms [1,2] thatdiffer), these materials can be used both for quantum simulation and forquantum design. An important property of moiré materials is that their bandfilling factors can be tuned over large ranges without introducing chemicaldopants, simply by using electrical gates.
In addition to realizing Mott insulators, density waves, a varietyof different types of magnets, and superconductors – states of matter that arefamiliar from the study of strongly correlated atomic scale cyrstals – moirematerials have emerged as perhaps the best plaform uncovered to date forstudies of topologically non-trivial matter, especially strongly interactingtopologically non-trivial matter. Therole of band topology is natural in graphene moires, where it derives from theinteresting band topology of graphene monolayers, but has been an unexpectedbonus [3] in the case of TMD moires where it derives from twists in the layerdegree of freedom. I will discuss someof the latest developments in this evolving story.
[1] R. Bistritzer, and A.H.MacDonald, Proceedings of the NationalAcademy of Sciences 26, 12233 ( 2011).
[2] F. Wu, T. Lovorn, E. Tutuc, and A.H.MacDonald, Phys. Rev. Lett. 121,026402 (2018).
[3] F. Wu, T. Lovorn, E.Tutuc, I. Martin, and A.H.MacDonald, Phys. Rev. Lett. 122, 086402 (2019).