Researchers devise tunable conducting edge

In their experiments, the researchers stacked monolayer WTe2 with Cr2Ge2Te6, or
CGT. Credit: Shi lab/UC Riverside

A research team led by a physicist at the University of California, Riverside, has demonstrated a new magnetized state in a monolayer of tungsten ditelluride, or WTe2, a new quantum material. Called a magnetized or ferromagnetic quantum spin Hall insulator, this material of one-atom thickness has an insulating interior but a conducting edge, which has important implications for controlling electron flow in nanodevices.

In a typical conductor, electrical current flows evenly everywhere. Insulators, on the other hand, do not readily conduct electricity. Ordinarily, monolayer WTe2 is a special insulator with a conducting edge; magnetizing bestows upon it more unusual properties.

“We stacked monolayer WTe2 with an insulating ferromagnet of several atomic layer thickness — of Cr2Ge2Te6, or simply CGT — and found that the WTe2 had developed ferromagnetism with a conducting edge,” said Jing Shi, a distinguished professor of physics and astronomy at UCR, who led the study. “The edge flow of the electrons is unidirectional and can be made to switch directions with the use of an external magnetic field.”

Shi explained that when only the edge conducts electricity, the size of the interior of the material is inconsequential, allowing electronic devices that use such materials to be made smaller — indeed, nearly as small as the conducting edge. Because devices using this material would consume less power and dissipate less energy, they could be made more energy efficient. Batteries using this technology, for example, would last longer.

Exploring quantum electron highways with laser light

 The translucent crystal at the center of this illustration is a topological insulator, a quantum material where electrons (white dots) flow freely on its surface but not through its interior. By hitting a TI with powerful pulses of circularly polarized laser light (red spiral), SLAC and Stanford scientists generated harmonics that revealed what happens when the surface switches out of its quantum phase and becomes an ordinary insulator.
Credit: Greg Stewart/SLAC National Accelerator Laboratory

Topological insulators, or TIs, have two faces: Electrons flow freely along their surface edges, like cars on a superhighway, but can’t flow through the interior of the material at all. It takes a special set of conditions to create this unique quantum state – part electrical conductor, part insulator – which researchers hope to someday exploit for things like spintronics, quantum computing and quantum sensing. For now, they’re just trying to understand what makes TIs tick.

In the latest advance along those lines, researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University systematically probed the “phase transition” in which a TI loses its quantum properties and becomes just another ordinary insulator.

They did this by using spiraling beams of laser light to generate harmonics – much like the vibrations of a plucked guitar string – from the material they were examining. Those harmonics make it easy to distinguish what’s happening in the superhighway layer from what’s happening in the interior and see how one state gradually gives way to the other, they reported in Nature Photonics.

“The harmonics generated by the material amplify the effects we want to measure, making this a very sensitive way to see what’s going on in a TI,” said Christian Heide, a postdoctoral researcher with the Stanford PULSE Institute at SLAC who led the experiments.

How water turns into ice — with quantum accuracy

Researchers at Princeton University combined artificial intelligence and quantum mechanics to simulate what happens at the molecular level when water freezes. The result is the most complete simulation yet of the first steps in ice “nucleation,” a process important for climate and weather modeling.  

Video by Pablo Piaggi, Princeton University

A team based at Princeton University has accurately simulated the initial steps of ice formation by applying artificial intelligence (AI) to solving equations that govern the quantum behavior of individual atoms and molecules.

The resulting simulation describes how water molecules transition into solid ice with quantum accuracy. This level of accuracy, once thought unreachable due to the amount of computing power it would require, became possible when the researchers incorporated deep neural networks, a form of artificial intelligence, into their methods. The study was published in the journal Proceedings of the National Academy of Sciences.

“In a sense, this is like a dream come true,” said Roberto Car, Princeton’s Ralph W. *31 Dornte Professor in Chemistry, who co-pioneered the approach of simulating molecular behaviors based on the underlying quantum laws more than 35 years ago. “Our hope then was that eventually we would be able to study systems like this one, but it was not possible without further conceptual development, and that development came via a completely different field, that of artificial intelligence and data science.”

The ability to model the initial steps in freezing water, a process called ice nucleation, could improve accuracy of weather and climate modeling as well as other processes like flash-freezing food.

The new approach enables the researchers to track the activity of hundreds of thousands of atoms over time periods that are thousands of times longer, albeit still just fractions of a second, than in early studies.

Car co-invented the approach to using underlying quantum mechanical laws to predict the physical movements of atoms and molecules. Quantum mechanical laws dictate how atoms bind to each other to form molecules, and how molecules join with each other to form everyday objects.

NIST Researchers Develop Miniature Lens for Trapping Atoms

Graphical illustration of light focusing using a planar glass surface studded with millions of nanopillars (referred to as a metalens) forming an optical tweezer. (A) Device cross section depicts plane waves of light that come to a focus through secondary wavelets generated by nanopillars of varying size. (B) The same metalens is used to trap and image single rubidium atoms.
Credit: Sean Kelley/NIST

Atoms are notoriously difficult to control. They zigzag like fireflies, tunnel out of the strongest containers and jitter even at temperatures near absolute zero.

Nonetheless, scientists need to trap and manipulate single atoms in order for quantum devices, such as atomic clocks or quantum computers, to operate properly. If individual atoms can be corralled and controlled in large arrays, they can serve as quantum bits, or qubits — tiny discrete units of information whose state or orientation may eventually be used to carry out calculations at speeds far greater than the fastest supercomputer.

Researchers at the National Institute of Standards and Technology (NIST), together with collaborators from JILA — a joint institute of the University of Colorado and NIST in Boulder — have for the first time demonstrated that they can trap single atoms using a novel miniaturized version of “optical tweezers” — a system that grabs atoms using a laser beam as chopsticks.

Ordinarily, optical tweezers, which garnered the 2018 Nobel Prize in Physics, feature bulky centimeter-size lenses or microscope objectives outside the vacuum holding individual atoms. NIST and JILA have previously used the technique with great success to create an atomic clock.

In the new design, instead of typical lenses, the NIST team used unconventional optics — a square glass wafer about 4 millimeters in length imprinted with millions of pillars only a few hundreds of nanometers (billionths of a meter) in height that collectively act as tiny lenses. These imprinted surfaces, dubbed metasurfaces, focus laser light to trap, manipulate and image individual atoms within a vapor. The metasurfaces can operate in the vacuum where the cloud of trapped atoms is located, unlike ordinary optical tweezers.

A Nanokelvin Microwave Freezer for Molecules

A close view inside the main vacuum chamber of the NaK molecules experiment. In the middle four high-voltage copper wires are routed to an ultrahigh-vacuum glasscell where the ultracold polar molecules were produced.
Credit: Max Planck Institute of Quantum Optics

Researchers at the Max Planck Institute of Quantum Optics have developed a novel cooling technique for molecular gases. It makes it possible to cool polar molecules down to a few nanokelvin. The trick used by the team in Garching to overcome this hurdle is based on a rotating microwave field. It helps to stabilize the collisions between the molecules during cooling by means of an energetic shield. In this way, the Max Planck researchers succeeded in cooling a gas of sodium-potassium molecules to 21 billionths of a degree above absolute zero. In doing so, they set a new low-temperature record. In the future, the new technique will allow us to create and explore many forms of quantum matter that have not been experimentally accessible until now.

When a highly diluted gas is cooled to extremely low temperatures, bizarre properties are revealed. Thus, some gases form a so-called Bose-Einstein condensate - a type of matter in which all atoms move in unison. Another example is supersolidity: a state in which matter behaves like a frictionless fluid with a periodic structure. Physicists expect to find particularly diverse and revealing forms of quantum matter when cooling gases consisting of polar molecules. They are characterized by an uneven electrical charge distribution. Unlike free atoms, they can rotate, vibrate and attract or repel each other. However, it is difficult to cool molecular gases to ultra-low temperatures.

A team of researchers at the Max Planck Institute of Quantum Optics in Garching has now found a simple and effective way to overcome this roadblock. It is based on a rotating field of microwaves.

100000 and Counting Atomic Modeling Silicon

Jim Chelikowsky and recent Oden Institute PhD graduate, Kai-Hsin Liou, sitting in the Professor's Oden Institute office.
Credit: Oden Institute for Computational Engineering and Sciences

A new record has been set by the Oden Institute’s Center for Computational Materials for calculating the energy distribution function, or “density of states,” for over 100,000 silicon atoms, a first in computational materials science. Calculations of this kind enable greater understanding of both the optical and electronic properties of materials.

Jim Chelikowsky leads the Center for Computational Materials, which set a new standard for the number of atoms that can be modeled. They didn’t just raise the bar though. They smashed it – multiplying the previously held record number by a factor of 10.

Chelikowsky along with Oden Institute PhD graduate, Kai-Hsin Liou and postdoctoral fellow, Mehmet Dogan, led the team behind this significant technical advancement in atomic modeling. Working with silicon atoms, they increased the number that could be modeled simultaneously from around 10,000 to over 100,000.

One mathematical way to approach such complex systems is by describing solutions in sines and cosines. This is useful for crystalline matter because it is periodic and we know that the properties of a little piece of a crystal will inform the whole crystal.

Researchers expand understanding of vortex spread in superfluids

An illustration of a vortex tangle.
Credit: Wei Guo/FAMU-FSU College of Engineering

An international team of scientists featuring Florida State University researchers has developed a model that predicts the spread of vortices in so-called superfluids, work that provides new insight into the physics that govern turbulence in quantum fluid systems such as superfluid neutron stars.

In a paper published in Physical Review Letters, the researchers created a model that describes the spread and speed of tornado-like vortex tubes in superfluids. Vortex tubes are a key ingredient of turbulence, which is widely studied in classical physics. The motion of vortex tubes is relevant in a wide range of scenarios, such as the formation of hurricanes, the airborne transmission of viruses and the chemical mixing in star formation. But it is poorly understood in quantum fluids.

This work expands on a previous study that reported experimental results obtained in superfluid helium-4 within a narrow temperature range. Superfluids are liquids that can flow without resistance, and therefore without a loss of kinetic energy. When they are stirred, they form vortices that rotate indefinitely.

“By validating this model and showing that it describes the movement of vortices at a wide range of temperatures, we are confirming a universal rule for this phenomenon,” said Wei Guo, an associate professor of mechanical engineering at the FAMU-FSU College of Engineering. “This discovery may aid the development of advanced theoretical models of quantum fluid turbulence.”

New imaging technique to find out what happens in the brains of dogs and cats

In a preliminary experiment, Parkkonen held a quantum optical MEG sensor with his hand on his family cat’s, Roosa’s, head while she listened to simple sound sequences.
Credit: Professor Lauri Parkkonen / Aalto University

For years, Professor Lauri Parkkonen's team at Aalto University has been developing quantum optical sensors for measuring the brain's magnetic fields using a technique known as magnetoencephalography (MEG). In traditional MEG, the superconducting sensors operate at very low temperatures and need centimeters of thermal insulation, but the quantum optical sensors work at room temperature, so they can be placed directly on the surface of the head. This allows more accurate measurements of the brain’s magnetic fields.

Parkkonen and his team plan to use the new method to build on their earlier work measuring brain activity in cats and dogs. Now they plan to characterize the complexity of the temporal structures in sensory stimuli that cat and dog brains can track. Similar experiments in humans have found that our brain produces specific responses to deviations in complex structures only when we attend to the stimuli and become aware of the deviations. Once the technique is perfected, Parkkonen and his team plan to use it to make similar measurements in human babies.

The experiments will begin this autumn – though Parkkonen has already done some preliminary tests with his family cat, Roosa – and the project is expected to continue until 2026. The researchers hope that their findings will provide an unprecedented window onto the cognition of cats and dogs, and this could also help bridge the gap between our understanding of human brains and the brains of other mammals.

Rice lab’s quantum simulator delivers new insight

Rice physicists used ultracold atoms and a 1D channel of light to simulate electrons in 1D wires and study how two of their intrinsic properties — spin and charge — travel at different speeds. They used a laser beam (top left) to produce collective waves that rippled left to right along the wire over time (top to bottom), transporting either spin or charge. A spin wave is illustrated. Spins must point up (blue) or down (red), and atoms with opposite spin naturally arrange in an alternating up-down, up-down pattern (top row). The wave transports spin by sequentially exchanging adjacent up/down spins (shaded ovals). Researchers measured the speed of both spin waves and charge waves (not shown), demonstrating the two traveled at different speeds.
Illustration by Ella Maru Studio, provided courtesy of R. Hulet/Rice University

A quantum simulator at Rice University is giving physicists a clear look at spin-charge separation, the quantum world’s version of the magician’s illusion of sawing a person in half.

Published this week in Science, the research has implications for quantum computing and electronics with atom-scale wires.

Electrons are minuscule, subatomic particles that cannot be divided. Despite this, quantum mechanics dictates that two of their attributes — spin and charge — travel at different speeds in one-dimensional wires.

Rice physicists Randy Hulet, Ruwan Senaratne and Danyel Cavazos built an ultracold venue where they could repeatedly view and photograph a pristine version of this quantum spectacle, and they collaborated with theorists from Rice, China, Australia and Italy on the published results.

Glimpses of Quantum Computing Phase Changes Show Researchers the Tipping Point

Tuning a quantum computer’s measurement rate provides hints of quantum phase transition

Researchers at Duke University and the University of Maryland have used the frequency of measurements on a quantum computer to get a glimpse into the quantum phenomena of phase changes – something analogous to water turning to steam.

By measuring the number of operations that can be implemented on a quantum computing system without triggering the collapse of its quantum state, the researchers gained insight into how other systems — both natural and computational — meet their tipping points between phases. The results also provide guidance for computer scientists working to implement quantum error correction that will eventually enable quantum computers to achieve their full potential.

The results appeared online in the journal Nature Physics.

When heating water to a boil, the movement of molecules evolves as the temperature changes until it hits a critical point when it starts to turn to steam. In a similar fashion, a quantum computing system can be increasingly manipulated in discrete time steps until its quantum state collapses into a single solution.

“There are deep connections between phases of matter and quantum theory, which is what’s so fascinating about it,” said Crystal Noel, assistant professor of electrical and computer engineering and physics at Duke. “The quantum computing system is behaving in the same way as quantum systems found in nature — like liquid changing to steam — even though it’s digital.”

Photon twins of unequal origin

The quantum dots of the Basel researchers are different, but send out exactly identical light particles.
Credit: University of Basel, Department of Physics

Researchers have created identical light particles with different quantum dots - an important step for applications such as tap-proof communication.

Many technologies that take advantage of quantum effects are based on exactly the same photons. However, it is extremely difficult to manufacture them. Not only must the wavelength (color) of the photons exactly match, but also their shape and polarization.

A team of researchers from the University of Basel around Richard Warburton, in collaboration with colleagues from the Ruhr University in Bochum, has now succeeded in producing identical photons that come from different, widely separated sources.

Individual photons from quantum dots

In their experiments, physicists use so-called quantum dots, i.e. structures a few nanometers in semiconductor materials. Electrons are trapped in these quantum dots, which only assume very specific energy levels and can emit light when moving from one level to another. With the help of a laser pulse that triggers such a transition, individual photons can be produced at the push of a button.

Perpetual motion is possible

Researchers cooled a helium-3 superfluid down to one ten-thousandth of a degree from absolute zero and proceeded to create two time-crystals inside the liquid.
Credit: Mikko Raskinen / Aalto University.

Professor and Nobel laureate in Physics Frank Wilczek, who also recently visited Aalto University to speak at a colloquium of Finland’s foremost quantum community InstituteQ, theorised the existence of time-crystals in 2012. They were experimentally confirmed to exist in 2016.

Now researchers have succeeded in creating and observing the interaction of two time-crystals in an experiment at Aalto University’s Low Temperature Lab.

The study was recently published in Nature Communications.

In an ordinary crystal the atoms or molecules comprising it have organized themselves into a regular crystal structure. Conversely, a time-crystal is a grouping of particles that moves without external energy, always returning to the same state in certain intervals. That means its regularity is expressed in time rather than in space.

‘Everyone knows perpetual motion machines are impossible. However, in quantum physics perpetual motion itself is possible as long as it’s not observed. By weakly connecting the particles to their environment, we were able to create up to two time-crystals and make them interact,’ says Samuli Autti, researcher at Lancaster University who carried out the experiment at Aalto.

Evasive quantum phenomenon makes debut in routine tabletop experiment

Researchers recently confirmed the presence of the axial Higgs mode, a particle excitation depicted here as a golden sphere. They used Raman spectroscopy, in which an incoming electric field, shown in blue, was coupled with the particle and subsequently scattered into a different frequency, shown in red.
 Credit: Ioannis Petrides and Prineha Narang/Harvard University

A Quantum Science Center-supported team has captured the first-ever appearance of a previously undetectable quantum excitation known as the axial Higgs mode.

This mode manifests as a low-energy excitation in rare-earth tellurides, a class of quantum materials notable for exhibiting charge density wave, or CDW, interactions. This behavior refers to arrangements of interacting electrons in quantum materials that form specific patterns and correlations.

Unlike the regular Higgs mode, which is produced by a Higgs mechanism that provides mass to fundamental particles in the Standard Model of Particle Physics, the axial Higgs mode is visible at room temperature. This characteristic enables more efficient and cost-effective experiments for manipulating quantum materials for various applications – including next-generation memory storage and opto-electronic devices – which would otherwise require extremely cold temperatures.

The team responsible for these results, which are published in Nature, was led by researchers at Boston College and includes scientists from Harvard University, Princeton University, University of Massachusetts Amherst, Yale University, University of Washington and the Chinese Academy of Sciences.

International team visualizes properties of plant cell walls at nanoscale

Scattering-type scanning near-field optical microscopy, a nondestructive technique in which the tip of the probe of a microscope scatters pulses of light to generate a picture of a sample, allowed the team to obtain insights into the composition of plant cell walls.
Credit: Ali Passian/ORNL, U.S. Dept. of Energy

To optimize biomaterials for reliable, cost-effective paper production, building construction, and biofuel development, researchers often study the structure of plant cells using techniques such as freezing plant samples or placing them in a vacuum. These methods provide valuable data but often cause permanent damage to the samples.

A team of physicists including Ali Passian, a research scientist at the Department of Energy’s Oak Ridge National Laboratory, and researchers from the French National Centre for Scientific Research, or CNRS, used state-of-the-art microscopy and spectroscopy methods to provide nondestructive alternatives. Using a technique called scattering-type scanning near-field optical microscopy, the team examined the composition of cell walls from young poplar trees without damaging the samples.

But the team still had other obstacles to overcome. Although plant cell walls are notoriously difficult to navigate due to the presence of complex polymers such as microfibrils — thin threads of biomass that Passian describes as a maze of intertwined spaghetti strings — the team reached a resolution better than 20 nanometers, or about a thousand times smaller than a strand of human hair. This detailed view allowed the researchers to detect optical properties of plant cell materials for the first time across regions large and small, even down to the width of a single microfibril. Their results were published in Communications Materials.

Bumps could smooth quantum investigations

Stamping or growing 2D materials onto a patterned surface could create models for 1D systems suitable for the exploration of quantum effects, according to a new theory by Rice University engineers. The “bumps” would manipulate the flow of electrons into bands that mimic 1D semiconductors.
Credit: Yakobson Research Group/Rice University

Atoms do weird things when forced out of their comfort zones. Rice University engineers have thought up a new way to give them a nudge.

Materials theorist Boris Yakobson and his team at Rice’s George R. Brown School of Engineering have a theory that changing the contour of a layer of 2D material, thus changing the relationships between its atoms, might be simpler to do than previously thought.

While others twist 2D bilayers -- two layers stacked together -- of graphene and the like to change their topology, the Rice researchers suggest through computational models that growing or stamping single-layer 2D materials on a carefully designed undulating surface would achieve “an unprecedented level of control” over their magnetic and electronic properties.

They say the discovery opens a path to explore many-body effects, the interactions between multiple microscopic particles, including quantum systems.

The paper by Yakobson and two alumni, co-lead author Sunny Gupta and Henry Yu, of his lab appears in Nature Communications.

Breakthrough paves way for photonic sensing at the ultimate quantum limit

Photonic chip with a microring resonator nanofabricated in a commercial foundry.
Photo credit: Joel Tasker, QET Labs

A Bristol-led team of physicists has found a way to operate mass manufacturable photonic sensors at the quantum limit. This breakthrough paves the way for practical applications such as monitoring greenhouse gases and cancer detection.

Sensors are a constant feature of our everyday lives. Although they often go unperceived, sensors provide critical information essential to modern healthcare, security, and environmental monitoring. Modern cars alone contain over 100 sensors and this number will only increase.

Quantum sensing is poised to revolutionize today's sensors, significantly boosting the performance they can achieve. More precise, faster, and reliable measurements of physical quantities can have a transformative effect on every area of science and technology, including our daily lives.

However, the majority of quantum sensing schemes rely on special entangled or squeezed states of light or matter that are hard to generate and detect. This is a major obstacle to harnessing the full power of quantum-limited sensors and deploying them in real-world scenarios.

Finding coherence in quantum chaos

A theoretical breakthrough in understanding quantum chaos could open new paths into researching quantum information and quantum computing, many-body physics, black holes, and the still-elusive quantum to classical transition.

“By applying balanced energy gain and loss to an open quantum system, we found a way to overcome a previously held limitation that assumed interactions with the surrounding environment would decrease quantum chaos,” said Avadh Saxena, a theoretical physicist at Los Alamos National Laboratory and member of the team that published the paper on quantum chaos in Physical Review Letters. “This discovery points to new directions in studying quantum simulations and quantum information theory.”

Quantum chaos differs from classical-physics chaos theory. The latter seeks to understand deterministic, or non-random, patterns and systems that are highly sensitive to initial conditions. The so-called butterfly effect is the most familiar example, whereby the flap of a butterfly’s wings in Texas could, through a bewilderingly complicated but not random chain of cause and effect, lead to a tornado in Kansas.

On the other hand, quantum chaos describes chaotic classical dynamical systems in terms of quantum theory. Quantum chaos is responsible for the scrambling of information occurring in complex systems such as blackholes. It reveals itself in the energy spectra of the system, in the form of correlations between its characteristic modes and frequencies.

It has been believed that as a quantum system loses coherence, or its “quantumness,” by coupling to the environment outside the system—the so-called quantum to classical transition—the signatures of quantum chaos are suppressed. That means they can’t be exploited as quantum information or as a state that can be manipulated.

‘Beam Me Up:’ Nation’s First Quantum Drone Provides Unrivaled Security

Hacked bank and Twitter accounts, malicious power outages and attempts to tamper with medical records threaten the security of the nation’s health, money, energy, society and infrastructure. Harnessing the laws of nature – namely quantum physics – cutting–edge teleportation technology is taking cybersecurity to new, “unhackable” heights using miniscule particles of light or “beams.”

Florida Atlantic University’s Warner A. Miller, Ph.D., in concert with Qubitekk and L3Harris, is leading the United States’ efforts to deliver the first drone-based, mobile quantum network to seamlessly maneuver around buildings, inclement weather and terrain and quickly adapt to changing environments such as warfare.

Together with Qubitekk, an award-winning leader in manufacturing entangled photon sources and other hardware for networking quantum processors and sensors, FAU has been entrusted by the U.S. Office of the Secretary of Defense to develop the project.

The network includes a ground station, drones, lasers and iber optics to share quantum-secured information. Today’s telecommunication networks use fiber optics, connected by laser beams from the ground and between planes and satellites — called fiber and free space optical networks. Drones are used to save lives, secure infrastructure, help the environment and thwart hostile military advances such as the war between Russia and Ukraine.

New tool measures atomic scale defects, identifies transistor limitations

Engineering science and mechanics doctoral student Fedor Sharov adjusts settings in a very low frequency EDMR spectrometer.
Credit: Kelby Hochreither/Penn State

A new technique for studying defects in semiconductor materials could lead to improved speed, power and performance of electronic devices by revealing the atomic-level limitations of advanced materials.

Developed by a Penn State-led team of researchers and lead by former Penn State graduate student James Ashton, the analytic tool makes use of extremely small magnetic fields and frequencies far smaller than those typically used in such measurements to detect and measure imperfections in new materials, providing structural information about the magnetic interactions between electrons and nearby magnetic nuclei in a simpler way than previously possible.

The approach was published as a cover article in Applied Physics Letters. According to Patrick Lenahan, distinguished professor of engineering science and mechanics at Penn State and Ashton’s doctoral thesis adviser, the tool allows researchers to take a big step toward solving a variety of faults in next-generation devices.

Spinning is key for line-dancing electrons in iron selenide

Quantum physicists Pengcheng Dai (left) and Qimiao Si outside Rice’s Brockman Hall for Physics in November 2021.
Photo by Jeff Fitlow/Rice University

Rice University quantum physicists are part of an international team that has answered a puzzling question at the forefront of research into iron-based superconductors: Why do electrons in iron selenide dance to a different tune when they move right and left rather than forward and back?

A research team led by Xingye Lu at Beijing Normal University, Pengcheng Dai at Rice and Thorsten Schmitt at the Paul Scherrer Institute (PSI) in Switzerland used resonant inelastic X-ray scattering (RIXS) to measure the behavior of electron spins in iron selenide at high energy levels.

Spin is the property of electrons related to magnetism, and the researchers discovered spins in iron selenide begin behaving in a directionally dependent way at the same time the material begins exhibiting directionally dependent electronic behavior, or nematicity. The team’s results were published online this week in Nature Physics.