The Extreme Quantum Materials Alliance (eQMA) is pleased to present the Fall 2024 eQMA Distinguished Lecture:
Moiré Materials
Allan MacDonald, University of Texas at Austin
October 23, 2024
4:00-5:00pm
Brockman 101
Reception to follow
Dr. MacDonald is Sid W. Richardson Foundation Regents Chair Professor of Physics at the University of Texas at Austin. He is the recipient of many honors, including American Physical Society’s Buckley Prize, the Wolf Prize and membership in the National Academy of Sciences.
Abstract:
Recent progress in fabricating two-dimensional material devices has created an opportunity to study the properties of quantum metamaterials in which electrons exhibit strongly-correlated and topologically non-trivial properties that are rare in naturally occurring crystals. For example, two-dimensional van der Waals crystals that are overlaid with a difference in lattice constant or a relative twist form a moiré pattern. In semiconductors and semimetals, the low-energy electronic properties of these systems are accurately described by Hamiltonians that have the periodicity of the moiré pattern – artificial crystals with lattice constants on the 10 nm scale. Since the miniband widths in both graphene and TMD moiré materials can be made small compared to interaction energy scales, by mechanisms that differ, these materials can be used both for quantum simulation and for quantum design. An important property of moiré materials is that their band filling factors can be tuned over large ranges without introducing chemical dopants, simply by using electrical gates.
In addition to realizing Mott insulators, density waves, a variety of different types of magnets, and superconductors – states of matter that are familiar from the study of strongly correlated atomic scale cyrstals – moiré materials have emerged as perhaps the best plaform uncovered to date for studies of topologically non-trivial matter, especially strongly interacting topologically non-trivial matter. The role of band topology is natural in graphene moiré, where it derives from the interesting band topology of graphene monolayers, but has been an unexpected bonus in the case of TMD moirés where it derives from twists in the layer degree of freedom. I will discuss some of the latest developments in this evolving story.