Light causes atomic layers to do the twist in moiré materials

Amazing stuff!

"In brief

• A new study shows that light can control the twisting motion of atomic layers in moiré materials, allowing for novel material manipulation techniques.
• Researchers used ultrafast electron diffraction to observe atomic dynamics in real time, offering groundbreaking insights into the behavior of materials.

...

A pulse of light sets the tempo in the material. Atoms in a crystalline sheet just a few atoms thick begin to move – not randomly, but in a coordinated rhythm, twisting and untwisting in sync like dancers following a beat. ..."

From the abstract:

"Two-dimensional moiré materials are formed by artificially stacking atomically thin monolayers. Correlated and topological quantum phases can be engineered by precise choice of stacking geometry. These designer electronic properties depend crucially on interlayer coupling and atomic registry. An open question is how the atomic registry responds on ultrafast timescales to optical excitation and whether the moiré geometry can be dynamically reconfigured to tune emergent phenomena in real time.

Here we show that femtosecond photoexcitation drives a coherent twist–untwist motion of the moiré superlattice in 2° and 57° twisted WSe2/MoSe2 heterobilayers, resolved directly by ultrafast electron diffraction.

On above-band-gap photoexcitation, the moiré superlattice diffraction features are enhanced within 1 ps and subsequently suppressed several picoseconds after, deviating markedly from typical photoinduced lattice heating.

Kinetic diffraction analysis, supported by simulations of the sample dynamics, indicates a peak-to-trough local twist angle modulation of 0.6°, correlated with a sub-THz frequency moiré phonon.

This motion is driven by ultrafast charge transfer that transiently increases interlayer attraction.

Our results could lead to ultrafast control of moiré periodic lattice distortions and, by extension, the local moiré potential that shapes excitons, polarons and correlation-driven behaviours."

Light causes atomic layers to do the twist | Stanford Report "A new study finds that light can control moiré materials, unlocking potential advances in superconductivity, magnetism, and quantum electronics."

Photoinduced twist and untwist of moiré superlattices (no public access)

Photoinduced twist and untwist of moiré superlattices in TMDC heterobilayers (preprint, open access)

Fawn Hallenbeck. Is she holding up an ancient Chinese mirror? 😊 Notice the bamboo in the background. Nice photo

Atom-by-atom imaging of moiré phasons or atomic thermal vibrations at a resolution of under 15 picometers

Amazing stuff! Good vibrations!

"A pioneering team ... has captured the first-ever images of atomic thermal vibrations, unlocking an unseen world of motion within two-dimensional materials. Their innovative electron ptychography technique revealed elusive “moiré phasons,” a long-theorized phenomenon that governs heat, electronic behavior, and structural order at the atomic level. This discovery not only confirms decades-old theories but also provides a new lens for building the future of quantum computing, ultra-efficient electronics, and advanced nanosensors. ..."

"Researchers investigating atomic-scale phenomena impacting next-generation electronic and quantum devices have captured the first microscopy images of atomic thermal vibrations—revealing a new type of motion that could reshape the design of quantum technologies and ultrathin electronics. ...

developed an electron microscopy technique to directly image “moiré phasons”—a physical phenomenon that impacts superconductivity and heat conduction in two-dimensional materials for next-generation electronic and quantum devices. ..."

From the abstract of the perspective:

"Twisted heterostructures—two atomically thin layers stacked at an angle by van der Waals forces—exhibit exotic properties beyond those of each layer alone, such as superconductivity.

The interlayer interactions cause structural reconstruction of atoms within the layers, forming a Moiré superlattice. This lattice has distinctive vibrational modes, called Moiré phonons (or phasons), that affect the material’s properties. However, low energy (~0.01 meV) and nanometer-scale spatial variation make the characterization of phasons with existing techniques extremely challenging. ...

Zhang et al. report the use of a computational imaging technique, called electron ptychography, to characterize phasons in twisted bilayers of tungsten diselenide. The findings illustrate how the extreme spatial resolution offered by electron ptychography can yield insights into a phenomenon that would be otherwise difficult to study."

From the editor's summary and abstract:

"Editor’s summary

The collective vibrations of a low-twist-angle moiré superlattice of tungsten diselenide were imaged with high-resolution electron ptychography. The rotationally aligned regions in these superlattices are separated by networks of stacking faults that can host ultrasoft shear modes, or phasons, with frequencies less than one wavenumber that are inaccessible using conventional vibrational spectroscopy. Imaging by Zhang et al. at a resolution of under 15 picometers revealed that these spatially localized, anisotropic vibrations dominated the thermal vibrations ...

Abstract

Twisted two-dimensional materials exhibit distinctive vibrational modes called moiré phonons, which arise from the moiré superlattice.

Here, we demonstrate atom-by-atom imaging of phasons, an ultrasoft class of moiré phonons in twisted bilayer tungsten diselenide (WSe2).

Using ultrahigh-resolution (<15 picometers) electron ptychography, we imaged the size and shape of each atom to extract time-averaged vibrational amplitudes as a function of twist angle and position.

We observed several signature properties of moiré phasons, such as increased vibrational amplitudes at solitons and AA-stacked regions. By correlating experiments with molecular dynamics simulations and lattice dynamics calculations, we show that phasons dominate the thermal vibrations in low-angle twisted bilayers. These results represent a powerful route to image thermal vibrations at atomic resolution, unlocking experimental studies of a thus far hidden branch of moiré phonon physics."

You’ve never seen atoms like this before: A hidden motion revealed | ScienceDaily

Scientists Document First Images of the Atomic Fingerprint of Heat in Quantum Materials (original news release)

Minuscule vibrations, uncovered (no public access) "Computational imaging resolves atomic vibrations at picometer scale"

Atom-by-atom imaging of moiré phasons with electron ptychography (no public access)

Atom-by-atom Imaging of Moiré Phasons using Electron Ptychography (preprint, open access)

The lead author Yichao Zhang

Metal layers just a few angstroms thick display unusual electronic properties

Amazing stuff!

"A new way to create ultra-thin layers of metals makes it possible for scientists to study a new and unusual class of 2D materials. Researchers in China used the technique to make layers of five different metals that were only a few angstroms thick, uncovering exotic physical properties. ...

The 6.3Å-thick bismuth sample is just two atoms deep and was stable for a whole year while the team tested its properties. The researchers noted that the bismuth sample shows strongly enhanced electrical conductivity, a notable field effect and a new and ‘prominent’ phonon mode. ..."

From the abstract:

"Two-dimensional (2D) metals are appealing for many emergent phenomena and have recently attracted research interests. Unlike the widely studied 2D van der Waals (vdW) layered materials, 2D metals are extremely challenging to achieve, because they are thermodynamically unstable.

Here we develop a vdW squeezing method to realize diverse 2D metals (including Bi, Ga, In, Sn and Pb) at the ångström thickness limit. The achieved 2D metals are stabilized from a complete encapsulation between two MoS2 monolayers and present non-bonded interfaces, enabling access to their intrinsic properties.

Transport and Raman measurements on monolayer Bi show excellent physical properties, for example, new phonon mode, enhanced electrical conductivity, notable field effect and large nonlinear Hall conductivity. Our work establishes an effective route for implementing 2D metals, alloys and other 2D non-vdW materials, potentially outlining a bright vision for a broad portfolio of emerging quantum, electronic and photonic devices."

Metal layers just a few angstroms thick display unusual electronic properties | Research | Chemistry World

Realization of 2D metals at the ångström thickness limit (no public access)

Atomic force microscopy image of a 2D bismuth sample consisting of the monolayer, bilayer and trilayer

The process of making the 2D metals involves squeezing them between sapphire anvils at high pressures

From a five-layer graphene sandwich, a rare electronic state emerges

The many wonders of graphene! Exotic properties all over.

"... Now, MIT physicists have discovered another surprising property in graphene: When stacked in five layers, in a rhombohedral pattern, graphene takes on a very rare, “multiferroic” state, in which the material exhibits both unconventional magnetism and an exotic type of electronic behavior, which the team has coined ferro-valleytricity. ...

The first ferroic property was an unconventional magnetism: The electrons coordinated their orbital motion, like planets circling in the same direction. (In conventional magnets, electrons coordinate their “spin” — rotating in the same direction, while staying relatively fixed in space.)

The second ferroic property had to do with graphene’s electronic “valley.” In every conductive material, there are certain energy levels that electrons can occupy. A valley represents the lowest energy state that an electron can naturally settle. As it turns out, there are two possible valleys in graphene. Normally, electrons have no preference for either valley and settle equally into both.

But in five-layer graphene, the team found that the electrons began to coordinate, and preferred to settle in one valley over the other. This second coordinated behavior indicated a ferroic property that, combined with the electrons’ unconventional magnetism, gave the structure a rare, multiferroic state. ..."

From the abstract:

"Ferroic orders describe spontaneous polarization of spin, charge and lattice degrees of freedom in materials. Materials exhibiting multiple ferroic orders, known as multiferroics, have important parts in multifunctional electrical and magnetic device applications. Two-dimensional materials with honeycomb lattices offer opportunities to engineer unconventional multiferroicity, in which the ferroic orders are driven purely by the orbital degrees of freedom and not by electron spin. These include ferro-valleytricity corresponding to the electron valley and ferro-orbital-magnetism supported by quantum geometric effects. These orbital multiferroics could offer strong valley–magnetic couplings and large responses to external fields—enabling device applications such as multiple-state memory elements and electric control of the valley and magnetic states. Here we report orbital multiferroicity in pentalayer rhombohedral graphene using low-temperature magneto-transport measurements. We observed anomalous Hall signals Rxy with an exceptionally large Hall angle (tanΘH > 0.6) and orbital magnetic hysteresis at hole doping. There are four such states with different valley polarizations and orbital magnetizations, forming a valley–magnetic quartet. By sweeping the gate electric field E, we observed a butterfly-shaped hysteresis of Rxy connecting the quartet. This hysteresis indicates a ferro-valleytronic order that couples to the composite field E · B (where B is the magnetic field), but not to the individual fields. Tuning E would switch each ferroic order independently and achieve non-volatile switching of them together. Our observations demonstrate a previously unknown type of multiferroics and point to electrically tunable ultralow-power valleytronic and magnetic devices."

From a five-layer graphene sandwich, a rare electronic state emerges | MIT News | Massachusetts Institute of Technology A newly discovered type of electronic behavior could help with packing more data into magnetic memory devices.

Orbital multiferroicity in pentalayer rhombohedral graphene (no public access, but article above contains a link to the open access version)

A Hidden phase Between Liquid And Solid May Have Been Found in 2d materials

Amazing stuff!

"Anything made out of plastic or glass is known as an amorphous material. Unlike many materials that freeze into crystalline solids, the atoms and molecules in amorphous materials never stack together to form crystals when cooled. In fact, although we commonly think of plastic and glass as “solids,” they instead remain in a state that is more accurately described as a supercooled liquid that flows extremely slowly. And although these “glassy dynamic” materials are ubiquitous in our daily lives, how they become rigid at the microscopic scale has long eluded scientists. ...

Specifically, using theory, computer simulations, and previous experiments, the scientists explained why the molecules in these materials, when cooled, remain disordered like a liquid until taking a sharp turn toward a solid-like state at a certain temperature called the onset temperature – effectively becoming so viscous that they barely move. This onset of rigidity – a previously unknown phase transition – is what separates supercooled from normal liquids. ...

Any supercooled liquid continuously jumps between multiple configurations of molecules, resulting in localized particle movements known as excitations. In their proposed theory ... treated the excitations in a 2D supercooled liquid as though they were defects in a crystalline solid. As the supercooled liquid’s temperature increased to the onset temperature, they propose that every instance of a bound pair of defects broke apart into an unbounded pair. At precisely this temperature, the unbinding of defects is what made the system lose its rigidity and begin to behave like a normal liquid. ..."

From the significance and the abstract:
"Significance

The dynamics of glass formers exhibit dramatic slowdown below an onset temperature that delineates the high-temperature and supercooled regimes. For two-dimensional (2D) glass formers, we propose that the onset temperature is described by a Kosterlitz–Thouless transition driven by the elastic excitations underlying the relaxation mechanism for glassy dynamics. Analogous to dislocation-mediated melting in 2D solids, the excitations exist as a bound dipole–dipole state in the supercooled regime and as free dipoles above the onset temperature. The Kosterlitz–Thouless scenario explains the elastic behavior of 2D supercooled liquids at intermediate timescales and thus, the Mermin–Wagner fluctuations observed in experiments and simulations of 2D glass formers. The present work reveals the exotic nature of 2D glass formers relevant to systems under extreme confinement.

Abstract

Below the onset temperature To, the equilibrium relaxation time of most glass-forming liquids exhibits glassy dynamics characterized by a super-Arrhenius temperature dependence. In this supercooled regime, the relaxation dynamics also proceeds through localized elastic excitations corresponding to hopping events between inherent states, i.e., potential-energy-minimizing configurations of the liquid. Despite its importance in distinguishing the supercooled regime from the high-temperature regime, the microscopic origin of To is not yet known. Here, we construct a theory for the onset temperature in two dimensions and find that an inherent-state melting transition, described by the binding–unbinding transition of dipolar elastic excitations, delineates the supercooled regime from the high-temperature regime. The corresponding melting transition temperature is in good agreement with the onset temperature found in various two-dimensional (2D) atomistic models of glass formers and an experimental binary colloidal system confined to a water–air interface. Additionally, we find the predictions for the renormalized elastic moduli to agree with the experimentally observed values for the latter 2D colloidal system. We further discuss the predictions of our theory on the displacement and density correlations at supercooled conditions, which are consistent with observations of the Mermin–Wagner fluctuations in experiments and molecular simulations."

A Hidden State Between Liquid And Solid May Have Been Found : ScienceAlert

Scientists Theorize a Hidden Phase Transition Between Liquid and a Solid Improved understanding of glassy dynamics could help scientists explain why a liquid behaves like a solid, and develop useful new materials

Inherent-state melting and the onset of glassy dynamics in two-dimensional supercooled liquids (open access)

(Left) Above an onset temperature, a 2D material exhibits normal liquid behavior with all particles similarly mobile (yellow). (Right) Below that temperature, it becomes supercooled, with the onset of rigidity leading to just some mobile particles (yellow) amongst solid-like ‘frozen’ regions (blue).

Physicists discover a new switch for superconductivity

Good news!

Why are Western countries wasting so much money and resources on so called renewable energy, which is intermittent, unreliable and an environmental disaster!

If humanity could harness nuclear fusion or superconductivity or both, Global Warming/Climate Change would be immediately relegated to the dustbin of history as one of the greatest follies/scams ever pursued by humans!

"... physicists have identified the key to how one class of superconductors undergoes a nematic transition, and it’s in surprising contrast to what many scientists had assumed. ...
The physicists made their discovery studying iron selenide (FeSe), a two-dimensional material that is the highest-temperature iron-based superconductor. The material is known to switch to a superconducting state  at temperatures as high as 70 kelvins ... Though still ultracold, this transition temperature is higher than that of most superconducting materials. ...
found that iron selenide shifts through an entirely new mechanism. Rather than undergoing a coordinated shift in spins, atoms in iron selenide undergo a collective shift in their orbital energy. It’s a fine distinction, but one that opens a new door to discovering unconventional superconductors. ..."

From the abstract:

"The origin of nematicity in FeSe remains a critical outstanding question towards understanding unconventional superconductivity in proximity to nematic order. To understand what drives the nematicity, it is essential to determine which electronic degree of freedom admits a spontaneous order parameter independent from the structural distortion. Here we use X-ray linear dichroism at the Fe K pre-edge to measure the anisotropy of the 3d orbital occupation as a function of in situ applied stress and temperature across the nematic transition. Along with using X-ray diffraction to precisely quantify the strain state, we reveal a lattice-independent, spontaneously ordered orbital polarization within the nematic phase, as well as an orbital polarizability that diverges as the transition is approached from above. These results provide strong evidence that spontaneous orbital polarization serves as the primary order parameter of the nematic phase."

Physicists discover a new switch for superconductivity | MIT News | Massachusetts Institute of Technology The results could help turn up unconventional superconducting materials.

Spontaneous orbital polarization in the nematic phase of FeSe (no public access)

A novel ultramicro supercapacitor with ultrahigh charge storage capability

Good news! Note that this research was published by the Indian Institute of Science and the senior author is a woman!

"Researchers at the Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (IISc), have designed a novel ultramicro supercapacitor, a tiny device capable of storing an enormous amount of electric charge. It is also much smaller and more compact than existing supercapacitors and can potentially be used in many devices ranging from streetlights to consumer electronics, electric cars and medical devices. ...
Supercapacitors, on the other hand, combine the best of both batteries and capacitors – they can store as well as release large amounts of energy, and are therefore highly sought-after for next-generation electronic devices.  ..."

From the abstract (notice the use of the word extraordinary twice):

"On-chip microscopic energy systems have revolutionized device design for miniaturized energy storage systems. Many atomically thin materials have provided a unique opportunity to develop highly efficient small-scale devices. We report an ultramicro-electrochemical capacitor with two-dimensional (2D) molybdenum disulphide (MoS2) and graphene-based electrodes. Due to the tunable density of states, 2D MoS2 provides electric field-induced doping and, combined with a graphene interface, leads to a high carrier mobility. The fabricated solid-state energy storage device is obtained using a gel electrolyte that provides an electrochemical capacitance of 1.8 mF/cm2. An extraordinary enhancement of ∼3000% in electrochemical capacitance (55 mF/cm2from 1.8 mF/cm2, measured from a cyclic voltammetry curve) is observed upon application of back-gate field of −25 V, which is more than the enhancement (18%) observed in a MoS2 electrochemical capacitor (0.95 mF/cm2 from 0.8 mF/cm2) without graphene, whereas the galvanic charge–discharge measurements analysis shows ∼1677% enhancement under the application of −25 V back-gate voltage. Thus, the electric field-induced doping in 2D MoS2, in addition to a high charge carrier mobility due to the graphene, plays a crucial role in an extraordinary large energy storage in the ultramicro-electrochemical capacitor. We also evaluated the capacitance response using an AC signal superimposed with the DC bias to investigate the influence of polarization potential on the electrolyte. The study provides a benchmark development of an ultramicro-electrochemical capacitor for ultrahigh charge storage capability."

Novel supercapacitor for energy storage applications

Gate Field Induced Extraordinary Energy Storage in MoS2-Graphene-Based Ultramicro-Electrochemical Capacitor (no public access)

Credits: A novel ultramicro supercapacitor with ultrahigh charge storage capability (I am not amused, this article almost copied the entire press release of the Indian Institute of Science without mentioning it or giving due credit)

Schematic of the device

Engineers grow “perfect” atom-thin 2D materials on industrial silicon wafers

Good news!

"... Enter 2D materials — delicate, two-dimensional sheets of perfect crystals that are as thin as a single atom. At the scale of nanometers, 2D materials can conduct electrons far more efficiently than silicon. The search for next-generation transistor materials therefore has focused on 2D materials as potential successors to silicon. ...
The team has developed a method that could enable chip manufacturers to fabricate ever-smaller transistors from 2D materials by growing them on existing wafers of silicon and other materials. The new method is a form of “nonepitaxial, single-crystalline growth,” which the team used for the first time to grow pure, defect-free 2D materials onto industrial silicon wafers. ...
With their method, the team fabricated a simple functional transistor from a type of 2D materials called transition-metal dichalcogenides, or TMDs, which are known to conduct electricity better than silicon at nanometer scales. ...
the researchers use conventional vapor deposition methods to pump atoms across a silicon wafer. The atoms eventually settle on the wafer and nucleate, growing into two-dimensional crystal orientations. If left alone, each “nucleus,” or seed of a crystal, would grow in random orientations across the silicon wafer. ... found a way to align each growing crystal to create single-crystalline regions across the entire wafer. ...

To do so, they first covered a silicon wafer in a “mask” — a coating of silicon dioxide that they patterned into tiny pockets, each designed to trap a crystal seed. Across the masked wafer, they then flowed a gas of atoms that settled into each pocket to form a 2D material — in this case, a TMD. The mask’s pockets corralled the atoms and encouraged them to assemble on the silicon wafer in the same, single-crystalline orientation. ... “You have single-crystalline growth everywhere, even if there is no epitaxial relation between the 2D material and silicon wafer.”

With their masking method, the team fabricated a simple TMD transistor and showed that its electrical performance was just as good as a pure flake of the same material.

They also applied the method to engineer a multilayered device. After covering a silicon wafer with a patterned mask, they grew one type of 2D material to fill half of each square, then grew a second type of 2D material over the first layer to fill the rest of the squares. The result was an ultrathin, single-crystalline bilayer structure within each square. ..."

MIT engineers grow “perfect” atom-thin materials on industrial silicon wafers | MIT News | Massachusetts Institute of Technology Their technique could allow chip manufacturers to produce next-generation transistors based on materials other than silicon.

Non-epitaxial single-crystal 2D material growth by geometric confinement (no public access)

By depositing atoms on a wafer coated in a “mask” (top left), ... can corral the atoms in the mask’s individual pockets (center middle), and encourage the atoms to grow into perfect, 2D, single-crystalline layers (bottom right).

Scientists Synthesize New Carbon Material: A Two-Dimensional Monolayer Polymeric Fullerene

Amazing stuff! It is a mouthful! I guess, even billions of years of evolution could not come up with such a material. 

This could be a breakthrough of more exotic materials to come with yet to be discovered novel properties.

"... Recently, scientists developed a new interlayer bonding cleavage strategy to prepare a two-dimensional monolayer polymeric fullerene. The research group was led by Prof. ZHENG Jian from the Institute of Chemistry of the Chinese Academy of Sciences (ICCAS)  ..."

From the abstract: 

"Two-dimensional (2D) carbon materials, such as graphene, have attracted particular attention owing to the exceptional carrier transport characteristics that arise from the unique π-electron system in their conjugated carbon network structure. To complement zero-bandgap graphene, material scientists have devoted considerable effort to identifying 2D carbon materials. However, it is a challenge to prepare large-sized single-crystal 2D carbon materials with moderate bandgaps. Here we prepare a single-crystal 2D carbon material, namely monolayer quasi-hexagonal-phase fullerene (C60), with a large size via an interlayer bonding cleavage strategy. In this monolayer polymeric C60, cluster cages of C60 are covalently bonded with each other in a plane, forming a regular topology that is distinct from that in conventional 2D materials. Monolayer polymeric C60 exhibits high crystallinity and good thermodynamic stability, and the electronic band structure measurement reveals a transport bandgap of about 1.6 electronvolts. Furthermore, an asymmetric lattice structure endows monolayer polymeric C60 with notable in-plane anisotropic properties, including anisotropic phonon modes and conductivity. This 2D carbon material with a moderate bandgap and unique topological structure offers an interesting platform for potential application in 2D electronic devices."

Scientists Synthesize New Carbon Material: A Two-Dimensional Monolayer Polymeric Fullerene

Synthesis of a monolayer fullerene network (no public access)

Physicists detect a hybrid particle held together by uniquely intense “glue”

Recommendable!

"In the particle world, sometimes two is better than one. Take, for instance, electron pairs [Cooper pairs]. When two electrons are bound together, they can glide through a material without friction, giving the material special superconducting properties. ...

Now ... physicists have detected another kind of hybrid particle in an unusual, two-dimensional magnetic material. They determined that the hybrid particle is a mashup of an electron and a phonon (a quasiparticle that is produced from a material’s vibrating atoms). When they measured the force between the electron and phonon, they found that the glue, or bond, was 10 times stronger than any other electron-phonon hybrid known to date.
The particle’s exceptional bond suggests that its electron and phonon might be tuned in tandem; for instance, any change to the electron should affect the phonon, and vice versa. In principle, an electronic excitation, such as voltage or light, applied to the hybrid particle could stimulate the electron as it normally would, and also affect the phonon, which influences a material’s structural or magnetic properties. Such dual control could enable scientists to apply voltage or light to a material to tune not just its electrical properties but also its magnetism.
The results are especially relevant, as the team identified the hybrid particle in nickel phosphorus trisulfide (NiPS3), a two-dimensional material that has attracted recent interest for its magnetic properties. If these properties could be manipulated, for instance through the newly detected hybrid particles, scientists believe the material could one day be useful as a new kind of magnetic semiconductor, which could be made into smaller, faster, and more energy-efficient electronics. ..."

From the abstract:

"In van der Waals (vdW) materials, strong coupling between different degrees of freedom can hybridize elementary excitations into bound states with mixed character. Correctly identifying the nature and composition of these bound states is key to understanding their ground state properties and excitation spectra. ...These results demonstrate NiPS3 as a platform to study strong interactions between spins, orbitals and lattice, and open pathways to coherent control of 2D magnets."

Physicists detect a hybrid particle held together by uniquely intense “glue” | MIT News | Massachusetts Institute of Technology The discovery could offer a route to smaller, faster electronic devices.

Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet (open access)

UCLA-led research team produces most accurate 3D images of ‘2D materials’

Amazing stuff!

"In the future, they [2D materials] could be the basis for semiconductors in ever smaller electronics, quantum computer components, more-efficient batteries, or filters capable of extracting freshwater from saltwater. ... For instance, when carbon is arranged in an atomically thin layer to form 2D graphene, it is stronger than steel, conducts heat better than any other known material, and has almost zero electrical resistance."

"The researchers showed that their 3D maps of the material’s atomic structure are precise to the picometer scale — measured in one-trillionths of a meter. They used their measurements to quantify defects in the 2D material, which can affect their electronic properties, as well as to accurately assess those electronic properties. ... The researchers examined a single layer of molybdenum disulfide, a frequently studied 2D material. In bulk, this compound is used as a lubricant. As a 2D material, it has electronic properties that suggest it could be employed in next-generation semiconductor electronics. The samples being studied were “doped” with traces of rhenium, a metal that adds spare electrons when replacing molybdenum."


UCLA-led research team produces most accurate 3D images of ‘2D materials’ | UCLA: Researchers used a new technology called scanning atomic electron tomography, which they developed.