Showing posts with label moiré. Show all posts
Showing posts with label moiré. Show all posts

Thursday, April 17, 2025

The Hofstadter Regime Converges Upon Us


AKA Fine-Tuning The Chaos Machine 

The above image is the perfect example of a moiré lattice and where it comes from. I noticed it while watching a lecture by a scientist cited below, for being the first to discover Hofstadter's Butterfly in real life. It's just the best image I've seen to explain what a moiré lattice is.

Credit: Graphene hBN Moire Lattices - taken from the presentation Bloch, Landau, and Dirac - Hofstadter's Butterfly in Graphene by Philip Kim - Kavli Inst 2018 [youtube link]

The perimeter of ignorance in science is also the front door of chaos theory. You could call it a lot of other things, most of which are listed in the tags for this post, but mostly, anything that's "too complicated" for us to understand right now, it's chaos-related. Discoveries in this field come from a bunch of different places, like interdimensional graphene, like topological operators, like epilepsy surgery.

Harnessing chaos: How the brain turns randomness into robust memory
Jan 2025, phys.org

Previous work on brain-imitating artificial intelligence systems known as neural networks suggested that injecting random fluctuations into their activity could actually improve their performance as they learned to perform a task. 

Noise appears to increase the amount of time it takes for inhibitory neuron connections with other neurons to weaken. This slowing effect in turn stabilizes neural patterns of activity related to memories, helping them persist over time.

(This whole thing makes me think very differently about background noise, and maybe even the idea of 'functional music')...

via Columbia Engineering Systems Intelligence Laboratory: Nuttida Rungratsameetaweemana et al, Random noise promotes slow heterogeneous synaptic dynamics important for robust working memory computation, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2316745122


How topology drives complexity in brain, climate and AI
Feb 2025, phys.org

Yes it does 

Transformative framework for understanding complex systems, using the new field of higher-order topological dynamics, and creating a connection between topological structures and emergent behavior. This comes from the field of information theory, and combines fusion of topology, higher-order networks, and non-linear dynamics.

via University of London: Ana P. Millán et al, Topology shapes dynamics of higher-order networks, Nature Physics (2025). DOI: 10.1038/s41567-024-02757-w

(Many body problem and higher order networks are the same thing - "interactions that extend beyond simple pairwise relationships".)

Most of us need to know: Hofstadter's butterfly (1976) was discovered before Mandelbrot coined the term "fractal" (1980), so he didn't know what to call it.

Hofstadter's butterfly: Quantum fractal patterns visualized
Feb 2025, phys.org

"Our discovery was basically an accident. We didn't set out to find this."

This is the first time Hofstadter's butterfly has been directly observed experimentally in a real material.

It was found using a moiré lattice - they were investigating superconductivity in twisted bilayer graphene, and when you hear twisted layers, you know we're also talking magic angle sandwiches. They used a scanning tunneling microscope to image moiré crystals at atomic resolution and examine their electron energy levels. The microscope works by bringing a sharp metallic tip less than a nanometer from the surface to allow quantum "tunneling" of electrons from the tip to the sample.

via Princeton University: Kevin P. Nuckolls et al, Spectroscopy of the fractal Hofstadter energy spectrum, Nature (2025). DOI: 10.1038/s41586-024-08550-2


Fitness centrality: New tool finds critical points in everything from cybersecurity to ecological conservation
Jan 2025, phys.org

The Vienna Complexity hub making waves

This approach is particularly good at finding nodes that, if removed, would isolate many other parts of the network—similar to a server failure interrupting the connection of many users in a communication network or a pump failure in a water supply network paralyzing the supply of water to districts.

Species in ecological networks, nodes in cybersecurity, roads in transportation networks. That's great. But it's people where this really has impact. Imagine trying to disable a social movement that could disturb the social fabric of a nation. You find the people, the nodes, at the center of the social network, and ... remove them, let's say. 

via Complexity Science Hub Vienna: Vito D P Servedio et al, Fitness centrality: a non-linear centrality measure for complex networks, Journal of Physics: Complexity (2025). DOI: 10.1088/2632-072X/ada845

Sunday, February 2, 2025

Graphene's End


Since its discovery in 2004, graphene has been heralded as the wonder material of the 21st century, and has been featured here quite often. It's spawned a whole new field of science basically, and it's called metameterials science, based on what's called two-dimensional materials. Twenty years later, we've reached peak graphene, with the news now being taken over by all things -ene, such as goldene or borophene, as seen below:

'Better than graphene' material development may improve implantable technology
May 2024, phys.org
https://phys.org/news/2024-05-graphene-material-implantable-technology.html

Borophene - It's the new graphene, impregnated with boron atoms, which makes it do even crazier things than graphene.

via Pennsylvania State University: Teresa Aditya et al, Chiral Induction in 2D Borophene Nanoplatelets through Stereoselective Boron–Sulfur Conjugation, ACS Nano (2024). DOI: 10.1021/acsnano.4c01792

Image credit: I can find no other credits except for a "3D-news" but this image is possibly related to 2010 Nobel Prize winner Andre Geim, who discovered graphene at University of Manchester in 2004. 


Electric fields boost graphene's potential, study shows
Jun 2024, phys.org

From the home of graphene, Manchester University:
"We demonstrate that electric field effects can disentangle and accelerate electrochemical processes in 2D crystals. This could be combined with state-of-the-art catalysts to efficiently drive complex processes like CO2 reduction, which remain enormous societal challenges."

"Control of these processes gives our graphene devices dual functionality as both memory and logic gate. This paves the way for new computing networks that operate with protons. This could enable compact, low-energy analog computing devices."

via University of Manchester National Graphene Institute: Jincheng Tong et al, Control of proton transport and hydrogenation in double-gated graphene, Nature (2024). DOI: 10.1038/s41586-024-07435-8.


Post Script: Moiré lattices is where you go when graphene ends, so:
Twist-angle in moiré lattice controls valley polarization switching in heterostructures
May 2024, phys.org

In case you were wondering, "they demonstrated for the first time the dependence of valley polarization switching and polarization degree on the moiré period by twist engineering in electrically controlled transition metal dichalcogenide heterobilayers". 

via Institute of Physics of the Chinese Academy of Sciences and Prof. Xu Xiulai of Peking University: Danjie Dai et al, Twist angle–dependent valley polarization switching in heterostructures, Science Advances (2024). DOI: 10.1126/sciadv.ado1281

Wednesday, September 11, 2024

The Graphene Legacy


Graphene was first discovered around 2004, and since then it's changed the world of science in ways far greater than most materials ever discovered. But we're at the point now where it's time to move on. Seeing the word "graphene" in a headline is no longer enough to make you want to see what it's doing. 

There's graphene but made of gold (goldene), there's something better than graphene (made of boron nitride), and there's the moiré lattice phenomena, which seems about as mindblowing as graphene itself was twenty years ago. 

Here are a few examples of how we're going ahead into the post-graphene world, and from now on, news about graphene will be limited to make for other things:

Researchers put a new twist on graphite
Jul 2023, phys.org

Didn't see this one coming!

They placed a single layer of graphene on top of a thin, bulk graphite crystal, and then introduced a twist angle of around 1 degree between graphite and graphene. They detected novel and unexpected electrical properties not just at the twisted interface, but deep in the bulk graphite as well. The electrical properties of the whole material differed markedly from typical graphite.

"Though we were generating the moiré pattern only at the surface of the graphite, the resulting properties were bleeding across the whole crystal."

Also: "Interdimensional" means mixed dimensional materials, like embedding 2D graphene into 3D graphite.

via University of Washington, Osaka University and the National Institute for Materials Science in Japan: Matthew Yankowitz, Mixed-dimensional moiré systems of twisted graphitic thin films, Nature (2023). DOI: 10.1038/s41586-023-06290-3.


Navigating moiré physics and photonics with band offset tuning
Oct 2023, phys.org

They started with a mismatched silicon-based bilayer moiré superlattice and adjusted the band offset by varying the thickness of one layer of the superlattices, to find that the offset effectively controls the moiré flatbands.

via SPIE Society of Photo-Optical Instrumentation Engineers, University of Electronic Science and Technology of China, Anqing Normal University, Guangxi University, and Nankai University: Peilong Hong et al, Robust moiré flatbands within a broad band-offset range, Advanced Photonics Nexus (2023). DOI: 10.1117/1.APN.2.6.066001


Researchers create first functional semiconductor made from graphene
Jan 2024, phys.org

Where you been - world's first functional semiconductor made from graphene

via Georgia Institute of Technology: Walt de Heer, Ultrahigh-mobility semiconducting epitaxial graphene on silicon carbide, Nature (2024). DOI: 10.1038/s41586-023-06811-0. 


Unlocking exotic physics: Exploring graphene's topological bands in super-moiré structures
Apr 2024, phys.org

Super-Moiré all day 

They're sandwiching monolayer graphene between two bulk boron nitride layers to create a new structure known as a super-moiré structure (whereas regular moiré is just two graphene layers).

via National University of Singapore:  Mohammed M. Al Ezzi et al, Topological Flat Bands in Graphene Super-Moiré Lattices, Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.126401.


A single atom layer of gold—researchers create goldene
Apr 2024, phys.org
https://phys.org/news/2024-04-atom-layer-gold-goldene.html

Goldene - a sheet of gold only a single atom layer thick

via Linköping University: Synthesis of goldene comprising single-atom layer gold, Nature Synthesis (2024). DOI: 10.1038/s44160-024-00518-4

Monday, August 12, 2024

Keeping an Eye on the Fractal Frontier


Dimensions are not always whole numbers, they can be fractions too. Electrons are not always one single indivisible entity, but apparently they can be fractions of themselves. You too, the illusion of a persistent subjective self, fractions.

Fractal photonic anomalous Floquet topological insulators to generate multiple quantum chiral edge states
Dec 2023, phys.org

Fractal photonics - stable carriers for high-capacity quantum information transmission by carry multiple topologically protected quantum chiral edge states

Chinese Academy of Science: Meng Li et al, Fractal photonic anomalous Floquet topological insulators to generate multiple quantum chiral edge states, Light: Science & Applications (2023). DOI: 10.1038/s41377-023-01307-y



Study finds no evidence for fractal scaling in canopy surfaces across a diverse range of forest types
Jan 2024, phys.org

The way trees grow together do not resemble how branches grow on a single tree (called self-similarity or fractality).

Airborne laser scanning data from nine sites spread across Australia's Terrestrial Ecosystem Research Network. "We found that forest canopies are not fractal, but they are very similar in how they deviate from fractality, irrespective of what ecosystem they are in. Most ecosystems, like forests, will hit an upper limit—most likely determined by the maximum size of its organisms—beyond which their structure cannot vary freely anymore.

So it's scale, but not fractals. 

via University of Bristol: Fabian Jörg Fischer et al, No evidence for fractal scaling in canopy surfaces across a diverse range of forest types, Journal of Ecology (2023). DOI: 10.1111/1365-2745.14244


Electrons become fractions of themselves in graphene
Feb 2024, phys.org

"This five-layer graphene (pentalayer graphene) is a material system where many good surprises happen"

In very special states of matter, electrons can splinter into fractions of their whole. This phenomenon is known as "fractional charge", and known to physicists as the "fractional quantum Hall effect," is rare.

When five sheets of graphene are stacked like steps on a staircase, the resulting structure inherently provides just the right conditions for electrons to pass through as fractions of their total charge, with no need for any external magnetic field.

The results are the first evidence of the "fractional quantum anomalous Hall effect"

The pentalayer structure were aligned with hexagonal boron nitride (hBN) to produce a moiré superlattice that could slow electrons down in ways that mimic a magnetic field.

"The day we saw it, we didn't recognize it at first," says first author Lu. "Then we started to shout as we realized, this was really big. It was a completely surprising moment."

via Massachusetts Institute of Technology: Long Ju, Fractional quantum anomalous Hall effect in multilayer graphene, Nature (2024). DOI: 10.1038/s41586-023-07010-7.


Discovery of the first fractal molecule in nature
Apr 2024, phys.org

The first regular molecular fractal in nature. They discovered a microbial enzyme - citrate synthase from a cyanobacterium - that spontaneously assembles into a pattern known as the Sierpinski triangle.

"We stumbled on this structure completely by accident and almost couldn't believe what we saw when we first took images of it using an electron microscope" 

via Max Planck Institute in Marburg and the Philipps University in Marburg: Franziska L. Sendker et al, Emergence of fractal geometries in the evolution of a metabolic enzyme, Nature (2024). DOI: 10.1038/s41586-024-07287-2

Tuesday, November 28, 2023

Words, for the Corpus That Has It All


The following update to the 'list of crazy words you read when scanning science press headlines', 6 months from April 2023 to October 2023. This one is a big list, an avalanche of verbal programming; start your semantic engines.

Appropriately illustrated by artificial intelligence engine-generated images of Dental Art, starting with the above image, prompted by the words "Hyperrealistic pink tissue bloody gums slippery glistening" but I just call it Dental Art.


Researchers develop the first-ever ingestible electroceutical device to control appetite by hormone modulation
Apr 2023, phys.org

"Electroceuticals" - for the neuromodulation of the gut-brain axis 

via NYU: Khalil Ramadi et al, Bioinspired, ingestible electroceutical capsules for hunger-regulating hormone modulation, Science Robotics (2023). DOI: 10.1126/scirobotics.ade9676.


Meteosat-12: Europe's new weather satellite takes first photos
Apr 2023, BBC News

"Nowcasting" - (like forecasting but better) the ability to say with greater confidence that violent winds, lightning, hail or heavy downpours are about to strike a particular area; Europe's new weather satellite Meteosat-12 flies 36,000km above the Earth and takes pictures every 10 minutes

And the word nowcasting, in the wild: "The insights gained from linking lightning intensity to eruptive activity can provide better monitoring and nowcasting of aviation-related hazards during a large volcanic eruption, including ash cloud development and movement," Van Eaton said." -New study shows Tonga's Hunga eruption produced the most intense lightning ever recorded. Jun 2023. phys.org
https://phys.org/news/2023-06-tonga-hunga-eruption-intense-lightning.html ; and via American Geophysical Union: Alexa R. Van Eaton et al, Lightning Rings and Gravity Waves: Insights Into the Giant Eruption Plume From Tonga's Hunga Volcano on 15 January 2022, Geophysical Research Letters (2023). DOI: 10.1029/2022GL102341. https://dx.doi.org/10.1029/2022GL102341


'Bioprospecting' technique uncovers viruses that can kill deadly superbugs
May 2023, phys.org

"Bioprospecting" for viruses known as phages that can kill deadly superbugs; like "bioprospector" will be a word on someone's resume soon

via Monash University: Rhys A. Dunstan et al, Epitopes in the capsular polysaccharide and the porin OmpK36 receptors are required for bacteriophage infection of Klebsiella pneumoniae, Cell Reports (2023). DOI: 10.1016/j.celrep.2023.112551


DarkBERT learns language of the Dark Web
May 2023, phys.org

Fucking "DarkBERT" - A Language Model for the Dark Side of the Internet

FYI - "Surface Web content" (as opposed to "Dark Web content") I think what this is saying, without saying it, is that the internet is English, but the Dark Web is not, so they can't use the internet as their training model like we do with all the others.

via Institute for Critical Infrastructure Technology: Youngjin Jin et al, DarkBERT: A Language Model for the Dark Side of the Internet, arXiv (2023). DOI: 10.48550/arxiv.2305.08596



Combining twistronics with spintronics could be the next giant leap in quantum electronics
Jun 2023, phys.org

I try to keep up, but -- "Twistronics", "spintronics", and "tunable moiré magnetism"

via Tohoku University: Guanghui Cheng et al, Electrically tunable moiré magnetism in twisted double bilayers of chromium triiodide, Nature Electronics (2023). DOI: 10.1038/s41928-023-00978-0


Researchers grow bio-inspired polymer brains for artificial neural networks
Jul 2023, phys.org

Neuromorphic "wetware" - based on memristive devices via electropolymerization aka growing wires

via Osaka University and Hokkaido University: Naruki Hagiwara et al, Fabrication and Training of 3D Conductive Polymer Networks for Neuromorphic Wetware, Advanced Functional Materials (2023). DOI: 10.1002/adfm.202300903


New study reveals why defense against brain corrosion declines in people with Alzheimer's disease
Jul 2023, phys.org

"Brain corrosion" - Why yes, oxidative stress corrodes the brain, and that's called oxidative damage. Some might even call it "rust", brain rust. 

via Case Western Reserve University: Sara Cazzaro et al, Slingshot homolog-1–mediated Nrf2 sequestration tips the balance from neuroprotection to neurodegeneration in Alzheimer's disease, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2217128120



Photonic time crystals could open the door to a new branch of optics
Jul 2023, phys.org

"Photonic Time Crystals" - they are the temporal version of photonic crystals, and in the optical domain could have profound implications for the science of light, enabling truly disruptive applications in the future

Just for background, and because this will all become the new computers of the next technological revolution -- "photonic crystals have a refractive index that oscillates periodically in space causing iridescence of precious minerals and insect wings for example."

via Technion-Israel Institute of Technology, Haifa, Israel, and Purdue University:  Eran Lustig et al, Time-refraction optics with single cycle modulation, Nanophotonics (2023). DOI: 10.1515/nanoph-2023-0126


Researchers put a new twist on graphite
Jul 2023, phys.org

"Interdimensional" - mixed dimensional materials, like embedding 2D graphene into 3D graphite

via University of Washington, Osaka University and the National Institute for Materials Science in Japan: Matthew Yankowitz, Mixed-dimensional moiré systems of twisted graphitic thin films, Nature (2023). DOI: 10.1038/s41586-023-06290-3.


Spontaneous quasi-crystal self-assembly observed using tiny vibrating magnetic spheres
Jul 2023, phys.org

"Spontaneous Crystals" aka "Spontaneous Quasi-Crystal Self-Assembly" - discovered sort of by accident

via Université Paris-Saclay: Andrea Plati et al, Quasi-crystalline order in vibrated granular matter, arXiv (2023). DOI: 10.48550/arxiv.2307.01643


Zentropy and the art of creating new ferroelectric materials
Aug 2023, phys.org

"Zentropy" - The "Z" in zentropy stands for the German word Zustandssumm, meaning "sum over states" of entropy, and alternatively considered a play on the term "zen" from Buddhism, and the idea is to consider how entropy can occur over multiple scales within a system to help predict potential outcomes of the system when influenced by its surroundings. It's also a parameter-free pathway to predicting how advanced materials behave. And in other words, it can integrate top-down statistical and bottom-up quantum mechanics to predict experimental measures of the system without "fitting parameters" to closely match real-world variables.

via Penn State: Zi-Kui Liu et al, Parameter-free prediction of phase transition in PbTiO3 through combination of quantum mechanics and statistical mechanics, Scripta Materialia (2023). DOI: 10.1016/j.scriptamat.2023.115480



Researchers use 'topological gardening' to achieve unexpected spin transport
Aug 2023, phys.org

Fastest forming word cluster in the sciences, that's all --

"Topological Gardening" - Although topological insulators conduct electricity only along their edges, and strictly in one direction, new science challenges that view by uncovering a new type of edge transport by manipulating edge states through bulk-edge interactions, similar to the pruning work done in gardening routines.

via Monash University: Yuefeng Yin et al, Extracting unconventional spin texture in two dimensional topological crystalline insulator bismuthene via tuning bulk-edge interactions, Materials Today Physics (2023). DOI: 10.1016/j.mtphys.2023.101168

Also: Qile Li et al, Localized Wannier function based tight-binding models for two-dimensional allotropes of bismuth, New Journal of Physics (2021). DOI: 10.1088/1367-2630/ac04c9


This fish doesn't just see with its eyes, it also sees with its skin
Aug 2023, phys.org

"Skin Vision" -- Hogfish can change color, and carry a gene for a light-sensitive protein called opsin that is activated in their skin, and that this gene is different from the opsin genes found in their eyes. Their skin is made of cells called chromatophores which contain pigment, with opsin proteins residing in a previously unknown cell type right underneath the chromatophore, which means that light striking the skin must pass through the pigment-filled chromatophores first before it reaches the light-sensitive layer, suggesting that their skin acts like internal Polaroid film, capturing changes in the light, so that they can "literally take a photo of their own skin from the inside".

via Duke University: Lorian Schweikert, Dynamic light filtering over dermal opsin as a sensory feedback system in fish color change, Nature Communications (2023). DOI: 10.1038/s41467-023-40166-4.


Scientists develop finger sweat test to detect antipsychotic drugs in patients
Aug 2023, phys.org

"Finger Sweat Test" - Scientists have now discovered a way to test the levels of common antipsychotic drugs (clozapine, quetiapine, or olanzapine) in the sweat from patients' fingerprints (and because blood tests are invasive and uncomfortable).

via University of Surrey: Noninvasive drug adherence monitoring of antipsychotic patients via finger sweat testing, Frontiers in Chemistry (2023). DOI: 10.3389/fchem.2023.1245089


Researchers prep fentanyl, heroin vaccines for human trials
Aug 2023, phys.org

"Heroin Vaccine" - Just the words heroin vaccine.

via University of Montana: Bethany Crouse et al, A TLR7/8 agonist increases efficacy of anti-fentanyl vaccines in rodent and porcine models, npj Vaccines (2023). DOI: 10.1038/s41541-023-00697-9


Crack vaccine research on rats could help babies of mothers who use cocaine—and reduce addiction
Oct 2023, phys.org

"Crack Vaccine" - Also. I have a feeling it doesn't end here. 

via Universidade Federal de Minas Gerais in Brazil: Rachel J. Stephenson et al, Anti-cocaine Vaccine Development: Where Are We Now and Where Are We Going?, Journal of Medicinal Chemistry (2023). DOI: 10.1021/acs.jmedchem.3c00366



Team simulates collective movement of worm blobs for future swarm robotic systems
Sep 2023, phys.org

"Swarm Ball", "Worm Ball", or "Swarm Robot Worm Ball" - systems of many individual components that must work collectively, using soft-bodied agents

(click on the article above for some high octane nightmare fuel)

via Tohoku University and Hiroshima University: Taishi Mikami et al, Elongating, entwining, and dragging: mechanism for adaptive locomotion of tubificine worm blobs in a confined environment, Frontiers in Neurorobotics (2023). DOI: 10.3389/fnbot.2023.1207374


Vulnerability to different COVID-19 mutations depends on previous infections and vaccination, study suggests
Oct 2023, phys.org

"Antigenic Cartography" - compares the similarity of different variants of the SARS-CoV-2 virus to measure how well human antibodies formed in response to infection with one virus respond to infection with a variant of that virus (and because they found that a person's immune response to SARS-CoV-2 depends on the variant they were previously exposed to)

via University of Cambridge's Center for Pathogen Evolution in the Department of Zoology: Samuel H. Wilks et al, Mapping SARS-CoV-2 antigenic relationships and serological responses, Science (2023). DOI: 10.1126/science.adj0070.



Next-generation printing: Precise and direct, using optical vortices
Oct 2023, phys.org

An "Optical Vortex Laser" - "Using a special laser beam known as an optical vortex, we have achieved stable printing of high-viscosity liquids that allows for the fabrication of microdroplet laser arrays and the micropatterning of conductive nanoinks, as well as bioinks for cell scaffolds, leading to the establishment of next-generation printed photonic or electronic devices."

via Osaka Metropolitan University:  Ken-ichi Yuyama et al, Fabrication of an Array of Hemispherical Microlasers Using Optical Vortex Laser-Induced Forward Transfer, ACS Photonics (2023). DOI: 10.1021/acsphotonics.3c01005


Photonic crystals bend light as though it were under the influence of gravity
Oct 2023, phys.org

"Pseudogravity" - replicating the effects of gravity

Also, they don't say moiré but they describe it: Kitamura and her colleagues modified photonic crystals by introducing lattice distortion; gradual deformation of the regular spacing of elements, which disrupted the grid-like pattern of protonic crystals. This manipulated the photonic band structure of the crystals, resulting in a curved beam trajectory in-medium—just like a light-ray passing by a massive celestial body such as a black hole.

via Tohoku University: Kanji Nanjyo et al, Deflection of electromagnetic waves by pseudogravity in distorted photonic crystals, Physical Review A (2023). DOI: 10.1103/PhysRevA.108.033522


Sabotage tool takes on AI image scrapers
Oct 2023, phys.org

"Data poisoning" - the tool named Nightshade manipulates image pixels that will alter the output during training but are not visible to the naked eye prior to processing. The tool is meant to "poison" graphics appropriated by AI companies to train image-generating models. "A moderate number of Nightshade attacks can destabilize general features in a text-to-image generative model, effectively disabling its ability to generate meaningful images," Zhao said. 

via University of Chicago: Shawn Shan et al, Prompt-Specific Poisoning Attacks on Text-to-Image Generative Models, arXiv (2023). DOI: 10.48550/arxiv.2310.13828

Tuesday, May 2, 2023

More Moiré


At the confluence of twisted magic angle nanosandwiches and the much bigger news of the accidental Kuhning of the universe comes an unlikely character, the moiré lattice.

It's a grid, the two-dimensional piece of molecular paper epitomized as the graphene sheet, but it's two of them sandwiched on top of each other, and then turning one slightly so the grid no longer matches up. It's like the chain link fence that creates undulating optical illusions when layered with another fence; these two nanosheets do weird things to the field that exist between them. 

Moiré lattices are being used to create weird crystals, so they're a big part of optoelectronics because crystals manipulate lasers. And they're also providing a novel model of physical interaction that's unexpectedly mirrored in the fabric of spacetime, which might give us a very different idea about how the universe works. 


New quasiparticle discovered in moiré patterns
Nov 2022, phys.org

They found an exciton in there - an electrically neutral quasiparticle that can carry energy and consists of an electron and electron "hole" that can be created for example by light impinging certain semiconductors and other materials.

Coming soon -  "post-silicon nanoscale optoelectronic devices"

via University of Texas at Austin: Mit H. Naik et al, Intralayer charge-transfer moiré excitons in van der Waals superlattices, Nature (2022). DOI: 10.1038/s41586-022-04991-9


Moiré superlattices show superpower in photonics and optoelectronics
Mar 2023, phys.org

"The era of moiré photonics and optoelectronics is coming."

Moiré superlattices are artificial quantum materials formed by vertically stacking two or more two-dimensional (2D) layered materials with a slight lattice mismatch and/or a small rotational twist. They introduce a potential landscape of much larger length scale than the crystal periodicity of the constituent 2D layers, providing a novel paradigm for engineering band structures and hence a plethora of exotic quantum phenomena.

via Chinese Academy of Sciences:  Luojun Du et al, Moiré photonics and optoelectronics, Science (2023). DOI: 10.1126/science.adg0014.

See also:

Post Script:
New one for me - "Ab initio" calculations ("from the beginning) are computations of electronic orbitals with no other hypotheses than Coulomb interactions between all electrons and nuclei with electrons obeying Fermi statistics with the Pauli exclusion principle.

Or - the only inputs into an ab initio calculation are physical constants; Ab initio quantum chemistry methods attempt to solve the electronic Schrödinger equation given the positions of the nuclei and the number of electrons [wiki]

Here's some examples:
Artist Frank Michielli does some cool fence-art