Frontiers in Synthetic Moiré Quantum Matter Proceedings of a Workshop (2022) / Chapter Skim
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8 Discussion Period
8 Discussion Period
Pages 84-92
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From page 84... ...
The panelists included the day's three presenters -- Ramamoorthy Ramesh of the University of California, Berkeley; Hemamala Karunadasa of Stanford University; and Marcel Franz of the University of British Columbia -- along with Pablo Jarillo-Herrero of the Massachusetts Institute of Technology, Jennifer Cano of Stony Brook University, and Ashvin Vishwanath of Harvard University, the first day's presenters. OVERVIEW Parkin began with the observation that moiré is a wonderful class of new materials with a large number of possible lattices.
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From page 85... ...
"I think it would be relatively straightforward," Parkin said, "to build automated systems to exfoliate and put these exfoliated sheets one on top of each other at different angles and build the next, next generation structures that were discussed by Pablo yesterday." Yet another approach that had been discussed on the workshop's first day, Parkin said, was to harness artificial intelligence and machine learning along with the "materials genome" project started about a decade ago to make predictions about which materials are likely to have which sorts of properties. Another key issue from the workshop, he said, has been the question of just how exotic the properties of moiré materials are.
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From page 86... ...
By contrast, the type of random access memory his group proposed in 1995 took a quarter of a century to make it to market. DISCUSSION To open the discussion period, Parkin asked the presenters if there were any points they would like to make before he began asking questions.
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From page 87... ...
There are many two-dimensional that have organic sheets templated with organic groups, she explained, and perhaps by choosing the organic groups wisely it will be possible to dictate how the layers come together, including the distance between the sheets and perhaps even the twist angle, based on simply the length of the link. In response to a clarifying question from Parkin, Karunadasa explained further that she was envisioning two different two-dimensional sheets, each with its own organic molecules attached, with the organic molecules chosen so that when the sheets were brought together, they would interact and create the desired twist.
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From page 88... ...
If we can devise some physical geometry where some moiré structure develops in three dimensions one could immediately start applying these tools that we're familiar with." A second way in which theorists can be useful, he added, is explaining observed phenomena, although that can take time. It took 40 years for theorists to explain superconductivity in ordinary metals, he said, and theorists are still working to explain the high-temperature superconductors discovered more than three decades ago, although there have been other phenomena -- such as the fractional quantum Hall effect -- that theorists were able to explain in years rather than decades.
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From page 89... ...
"For example, if an electron goes through a periodic magnetic system it looks to the electron like some kind of a spin–orbit coupling effect," he said. "So I think in this way, you could create artificial spin textures which could have interesting properties." Also, referring back to his previous comment about whether devices made from moiré materials might be impractically large to use in modern chip technology,
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From page 90... ...
"There's been a whole field where people are exploring these vari ous structures with topological properties for propagation of light, for propagation of acoustic waves, and all these phenomena," he said. "I have a feeling that these moiré structures and wave propagation phenomena are the next frontier." Jarillo-Herrero reported that people have already made moiré and twisted phononic systems where they can slow down the phonons as well as photonic lattices where light can be slowed down.
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From page 91... ...
This led to several other suggestions as to how a differential strain might be applied, depending on the materials -- with electric fields, magnetic fields, even light. Finally, touching on other potential applications, Parkin observed that if superconductivity can be turned on an off in these materials -- by applying strain or an electric field, say -- then they could be used to make sensitive transistors or switches.
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