Frontiers in Synthetic Moiré Quantum Matter Proceedings of a Workshop (2022) / Chapter Skim
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2 Theoretical Considerations Concerning Moiré Quantum Materials
2 Theoretical Considerations Concerning Moiré Quantum Materials
Pages 14-20
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From page 14... ...
There are hundreds of two-dimensional van der Waals materials that could serve as building blocks, he said, including insulators such as hexagonal boron nitride, various metals and semimetals, semiconductors, superconductors, ferroelectrics, and magnets and quantum spin liquids. "We can play with all of them." One recent publication, for example, reported on monolayer copper oxides used in a twisted double-layer structure which result in high-temperature topological superconductivity (Can et al.
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From page 15... ...
This has been done with silicon and many other materials, and it would be interesting to create new moiré structures with some films of exotic quantum materials that were not originally van der Waals materials. "You can play a lot of games with this moiré and with twisted structures," he said.
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From page 16... ...
In the case of the twisted stacked graphene, the electronic structures are clearly distinct up to at least six layers, but after that the first magic angle changes by smaller and smaller amounts with each additional layer, he said, "so I think probably six to seven layers is a realistic number." Kapitulnik then passed along two questions about the specific properties of electrons in the twisted multilayer graphene materials: Are spin interactions between the electrons important, and what is known about the type of superconductivity? Jarillo-Herrero answered that at this point there are no known mechanisms that would generate a large spin coupling between electrons, so "we suspect that for graphene-based moiré structures spin–orbit coupling is very small.
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From page 17... ...
2021. "Electric Field Tunable Superconductivity in Alternating Twist Magic-Angle Trilayer Graphene." Science 371(6534)
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From page 18... ...
To begin, Vishwanath offering some context for moiré quantum materials by looking back to an earlier breakthrough in condensed matter physics. The invention of transistors and other semiconductor devices, Vishwanath said, made it possible to replace the much bulkier, more expensive, and more energy-intensive vacuum tubes, which up to that point had been the main option for using an electric current to modulate a second current.
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From page 19... ...
Thus, he said, part of his presentation would describe recent work by his team "that has given us some insight into the flat bands at least in twisted bilayer graphene systems." That insight has allowed his team to go beyond to the multilayers that Jarillo-Harrero had discussed and beyond the triangle geometry and using some basic principles to engineer flat bands. In the second part of his talk, he said, he would discuss a wish list of models his group would like to realize in a controlled fashion.
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From page 20... ...
graphene except that now! at the magic angle the band is perfectly flat 0 (third energy band structure D⇤ (−r)
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