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Scandium is the only known elemental superconductor to have a critical temperature in the 30 K range. This phase diagram shows the superconducting transition temperature (T_c) and crystal structure versus pressure for scandium. The measured results on all the five samples studied show consistent trends. (Courtesy: Chinese Phys. Lett. 40 107403)

Topics: Applied Physics, Chemistry, Condensed Matter Physics, Materials Science, Superconductors, Thermodynamics

Scandium remains a superconductor at temperatures above 30 K (-243.15 Celsius, -405.67 Fahrenheit), making it the first element known to superconduct at such a high temperature. The record-breaking discovery was made by researchers in China, Japan, and Canada, who subjected the element to pressures of up to 283 GPa – around 2.3 million times the atmospheric pressure at sea level.

Many materials become superconductors – that is, they conduct electricity without resistance – when cooled to low temperatures. The first superconductor to be discovered, for example, was solid mercury in 1911, and its transition temperature T_c is only a few degrees above absolute zero. Several other superconductors were discovered shortly afterward with similarly frosty values of T_c.

In the late 1950s, the Bardeen–Cooper–Schrieffer (BCS) theory explained this superconducting transition as the point at which electrons overcome their mutual electrical repulsion to form so-called “Cooper pairs” that then travel unhindered through the material. But beginning in the late 1980s, a new class of “high-temperature” superconductors emerged that could not be explained using BCS theory. These materials have Tc above the boiling point of liquid nitrogen (77 K), and they are not metals. Instead, they are insulators containing copper oxides (cuprates), and their existence suggests it might be possible to achieve superconductivity at even higher temperatures.

The search for room-temperature superconductors has been on ever since, as such materials would considerably improve the efficiency of electrical generators and transmission lines while also making common applications of superconductivity (including superconducting magnets in particle accelerators and medical devices like MRI scanners) simpler and cheaper.

Scandium breaks temperature record for elemental superconductors, Isabelle Dumé, Physics World

Credit: CC0 Public Domain

Topics: Condensed Matter Physics, Materials Science, Quantum Computer, Quantum Mechanics

Quantum scientists have discovered a rare phenomenon that could hold the key to creating a 'perfect switch' in quantum devices, which flips between being an insulator and a superconductor.

The research, led by the University of Bristol and published in Science, found these two opposing electronic states exist within purple bronze, a unique one-dimensional metal composed of individual conducting chains of atoms.

Tiny changes in the material, for instance, prompted by a small stimulus like heat or light, may trigger an instant transition from an insulating state with zero conductivity to a superconductor with unlimited conductivity and vice versa. This polarized versatility, known as "emergent symmetry," has the potential to offer an ideal On/Off switch in future quantum technology developments.

Lead author Nigel Hussey, Professor of Physics at the University of Bristol, said, "It's a really exciting discovery that could provide a perfect switch for quantum devices of tomorrow.

"The remarkable journey started 13 years ago in my lab when two Ph.D. students, Xiaofeng Xu, and Nick Wakeham, measured the magnetoresistance—the change in resistance caused by a magnetic field—of purple bronze."

In the absence of a magnetic field, the resistance of purple bronze was highly dependent on the direction in which the electrical current was introduced. Its temperature dependence was also rather complicated. Around room temperature, the resistance is metallic, but as the temperature is lowered, this reverses and the material appears to be turning into an insulator. Then, at the lowest temperatures, the resistance plummets again as it transitions into a superconductor.

Despite this complexity, surprisingly, the magnetoresistance was found to be extremely simple. It was essentially the same irrespective of the direction in which the current or field was aligned and followed a perfect linear temperature dependence all the way from room temperature down to the superconducting transition temperature.

Research reveals rare metal could offer revolutionary switch for future quantum devices, Queen's University Belfast, Phys.org.

Fractals are a never-ending pattern that you can zoom in on, and the image doesn’t change. Fractals can occur in two dimensions, like frost on a window, or in three dimensions, like tree limbs. A recent discovery from Purdue University researchers has established that superconducting images, seen above in red and blue, are actually fractals that fill a three-dimensional space and are disorder driven rather than driven by quantum fluctuations as expected. Frost and tree images by Adobe. Superconducting image (center) from "Critical nematic correlations throughout the superconducting doping range in Bi_2-xPb_zSr_2-yLa_yCuO_6+x" in Nature Communications. Credit: Nature Communications (2023). DOI: 10.1038/s41467-023-38249-3

Topics: Applied Physics, Civilization, Computer Modeling, Condensed Matter Physics, Materials Science, Solid-State Physics, Superconductors

Meeting the world's energy demands is reaching a critical point. Powering the technological age has caused issues globally. It is increasingly important to create superconductors that can operate at ambient pressure and temperature. This would go a long way toward solving the energy crisis.

Advancements with superconductivity hinge on advances in quantum materials. When electrons inside quantum materials undergo a phase transition, the electrons can form intricate patterns, such as fractals. A fractal is a never-ending pattern. When zooming in on a fractal, the image looks the same. Commonly seen fractals can be a tree or frost on a windowpane in winter. Fractals can form in two dimensions, like the frost on a window, or in three-dimensional space, like the limbs of a tree.

Dr. Erica Carlson, a 150th Anniversary Professor of Physics and Astronomy at Purdue University, led a team that developed theoretical techniques for characterizing the fractal shapes that these electrons make in order to uncover the underlying physics driving the patterns.

Carlson, a theoretical physicist, has evaluated high-resolution images of the locations of electrons in the superconductor Bi_2-xPb_zSr_2-yLa_yCuO_6+x (BSCO) and determined that these images are indeed fractal and discovered that they extend into the full three-dimensional space occupied by the material, like a tree filling space.

What was once thought of as random dispersions within the fractal images are purposeful and, shockingly, not due to an underlying quantum phase transition as expected but due to a disorder-driven phase transition.

Carlson led a collaborative team of researchers across multiple institutions and published their findings, titled "Critical nematic correlations throughout the superconducting doping range in Bi_2-xPb_zSr_2-yLa_yCuO_6+x," in Nature Communications.

The team includes Purdue scientists and partner institutions. From Purdue, the team includes Carlson, Dr. Forrest Simmons, a recent Ph.D. student, and former Ph.D. students Dr. Shuo Liu and Dr. Benjamin Phillabaum. The Purdue team completed their work within the Purdue Quantum Science and Engineering Institute (PQSEI). The team from partner institutions includes Dr. Jennifer Hoffman, Dr. Can-Li Song, Dr. Elizabeth Main of Harvard University, Dr. Karin Dahmen of the University of Illinois at Urbana-Champaign, and Dr. Eric Hudson of Pennsylvania State University.

Researchers discover superconductive images are actually 3D and disorder-driven fractals, Cheryl Pierce, Purdue University, Phys.org.

A diamond anvil is used to put superconducting materials under high pressure. Credit: J. Adam Fenster/University of Rochester

Topics: Applied Physics, Condensed Matter Physics, Materials Science, Superconductors

Will a possible breakthrough for room-temperature superconducting materials hold up to scrutiny?

This week researchers claimed to have discovered a superconducting material that can shuttle electricity with no loss of energy under near-real-world conditions. But drama and controversy behind the scenes have many worried that the breakthrough may not hold up to scientific scrutiny.

“If you were to find a room-temperature, room-pressure superconductor, you’d have a completely new host of technologies that would occur—that we haven’t even begun to dream about,” says Eva Zurek, a computational chemist at the University at Buffalo, who was not involved in the new study. “This could be a real game changer if it turns out to be correct.”

Scientists have been studying superconductors for more than a century. By carrying electricity without shedding energy in the form of heat, these materials could make it possible to create incredibly efficient power lines and electronics that never overheat. Superconductors also repel magnetic fields. This property lets researchers levitate magnets over a superconducting material as a fun experiment—and it could also lead to more efficient high-speed maglev trains. Additionally, these materials could produce super strong magnets for use in wind turbines, portable magnetic resonance imaging machines, or even nuclear fusion power plants.

The only superconducting materials previously discovered require extreme conditions to function, which makes them impractical for many real-world applications. The first known superconductors had to be cooled with liquid helium to temperatures only a few degrees above absolute zero. In the 1980s, researchers found superconductivity in a category of materials called cuprates, which work at higher temperatures yet still require cooling with liquid nitrogen. Since 2015 scientists have measured room-temperature superconductive behavior in hydrogen-rich materials called hydrides. but they have to be pressed in a sophisticated viselike instrument called a diamond anvil cell until they reach a pressure of about a quarter to half of that found near the center of Earth.

The new material, called nitrogen-doped lutetium hydride, is a blend of hydrogen, the rare-earth metal lutetium, and nitrogen. Although this material also relies on a diamond anvil cell, the study found that it begins exhibiting superconductive behavior at a pressure of about 10,000 atmospheres—roughly 100 times lower than the pressures that other hydrides require. The new material is “much closer to ambient pressure than previous materials,” says David Ceperley, a condensed matter physicist at the University of Illinois at Urbana-Champaign, who was not involved in the new study. He also notes that the material remains stable when stored at a room pressure of one atmosphere. “Previous stuff was only stable at a million atmospheres, so you couldn’t really take it out of the diamond anvil” cell, he says. “The fact that it’s stable at one atmosphere of pressure also means that it’d be easier to manufacture.”

Controversy Surrounds Blockbuster Superconductivity Claim, Sophie Bushwick, Scientific American

Cross-section of a fulgurite sample showing fused sand and melted conductor metal from a downed powerline. Credit: Luca Bindi et al.

Topics: Condensed Matter Physics, Energy, Materials Science

A team of researchers from Università di Firenze, the University of South Florida, California Institute of Technology, and Princeton University has found an incidence of a quasicrystal formed during an accidental electrical discharge.

In their paper published in Proceedings of the National Academy of Sciences, the group describes their study of a quasicrystal found in a sand dune in Nebraska.

Quasicrystals, as their name suggests, are crystal-like substances. They possess characteristics not found in ordinary crystals, such as a non-repeating arrangement of atoms. To date, quasicrystals have been found embedded in meteorites and in the debris from nuclear blasts. In this new effort, the researchers found one embedded in a sand dune in Sand Hills, Nebraska.

A study of the quasicrystal showed it had 12-fold, or dodecagonal, symmetry—something rarely seen in quasicrystals. Curious about how it might have formed and ended up in the sand dune, the researchers did some investigating. They discovered that a power line had fallen on the dune, likely due to a lightning strike. They suggest the electrical surge from either the power line or the lightning could have produced the quasicrystal.

The researchers note that the quasicrystal was found inside a tubular piece of fulgurite. They suggest it was also formed during the electrical surge due to the fusing of melted sand and metal from the power line.

Quasicrystal formed during accidental electrical discharge, Bob Yirka, Phys.org

How can you tell if a material is a superconductor? Four classic signatures are illustrated here. Left to right: 1) It conducts electricity with no resistance when chilled below a certain temperature. 2) It expels magnetic fields, so a magnet placed on top of it will levitate. 3) Its heat capacity – the amount of heat needed to raise its temperature by a given amount – shows a distinctive anomaly as the material transitions to a superconducting state. 4) And at that same transition point, its electrons pair up and condense into a sort of electron soup that allows current to flow freely. Now experiments at SLAC and Stanford have captured this fourth signature in cuprates, which become superconducting at relatively high temperatures, and show that it occurs in two distinct steps and at very different temperatures. Knowing how that happens in fine detail suggests a new and very practical direction for research into these enigmatic materials. (Courtesy: Greg Stewart, SLAC National Accelerator Laboratory)

Topics: Condensed Matter Physics, Superconductor, Thermodynamics

Researchers in the US report that they have observed the so-called “fourth signature” of superconducting phase transitions in materials known as cuprates. The result, obtained via photoemission spectroscopy of a cuprate called Bi2212, could shed fresh light on how these materials, which conduct electricity without resistance at temperatures of 77 K or higher, transition into the superconducting state.

The superconducting transition occurs when a material loses all resistance to an electrical current below a certain critical temperature T_c. At this temperature, bulk materials exhibit four characteristic “signatures” – electrical, magnetic, thermodynamic, and spectroscopic – indicating that transition has occurred. The electrical signature is the development of zero resistance. The magnetic signature is the onset of the Meissner effect – that is, the material expels magnetic fields. And the thermodynamic signature is that the material’s heat capacity (the amount of heat required to increase its temperature by a given value) displays a distinctive anomaly.

Elusive superconducting-transition signature seen for the first time, Isabelle Dumé, Physics World

Topography of the two-dimensional crystal on top of the microscopically small wire indicated by dashed lines. Excitons freely move along the wire-induced dent, but cannot escape it in the perpendicular direction. (Courtesy: Florian Dirnberger)

Topics: Applied Physics, Condensed Matter Physics, Electrical Engineering

Using a technique known as strain engineering, researchers in the US and Germany have constructed an “excitonic wire” – a one-dimensional channel through which electron-hole pairs (excitons) can flow in a two-dimensional semiconductor like water through a pipe. The work could aid the development of a new generation of transistor-like devices.

In the study, a team led by Vinod Menon at the City College of New York (CCNY) Center for Discovery and Innovation and Alexey Chernikov at the Dresden University of Technology and the University of Regensburg in Germany deposited atomically thin 2D crystals of tungsten diselenide (fully encapsulated in another 2D material, hexagonal boride nitride) atop a 100 nm-thin nanowire. The presence of the nanowire created a small, elongated dent in the tungsten diselenide by slightly pulling apart the atoms in the 2D material and so inducing strain in it. According to the study’s lead authors, Florian Dimberger and Jonas Ziegler, this dent behaves for excitons much like a pipe does for water. Once trapped inside, they explain, the excitons are bound to move along the pipe.

Strain guides the flow of excitons in 2D materials, Isabelle Dumé, Physics World

(Credit: Giovanni Cancemi/Shutterstock) 

Topics: Biology, Condensed Matter Physics, Modern Physics, Quantum Mechanics

Note: After presenting my research proposal and acceptance by my committee, I've been taking a well-needed break from blogging. I'll post on and off until the New Year, which isn't too far off. Happy holidays!

In recent years, evidence has emerged that quantum physics seems to play a role in some of life’s fundamental processes. But just how it might do this is something of a mystery.

On the one hand, quantum phenomena are generally so delicate that they can only be observed when all other influences are damped – in other words in carefully controlled systems at temperatures close to absolute zero. By contrast, the conditions for life are generally complex, warm, and damp. Understanding this seemingly contradictory state of affairs is an important goal.

So physicists and biologists are keen to explore the boundaries of these very different regimes—life and quantum mechanics—to better understand where they might overlap.

Now Rainer Dumke at the Nanyang Technological University in Singapore and colleagues have created an exotic quantum state called entanglement using a superconducting qubit and a microscopic animal called a tardigrade. Along the way, the team has created the most extreme form of suspended animation ever recorded. “The tardigrade itself is shown to be entangled with the remaining subsystems,” they say.

To perform their entanglement experiment, Dumke and co cooled their tardigrade to below 10 millikelvins, almost to absolute zero, while reducing the pressure to a millionth of that in the atmosphere. In these conditions, no chemical reaction can occur so the tardigrade’s metabolism must have entirely halted stopped and the processes of life halted.

“This is to date the most extreme exposure to low temperatures and pressures that a tardigrade has been recorded to survive, clearly demonstrating that the state of cryptobiosis ultimately involves a suspension of all metabolic processes given that all chemical reactions would be prohibited with all its constituent molecules cooled to their ground states,” say the researchers.

In this condition, the tardigrade can be thought of as a purely dielectric element. Indeed, the researchers simulated their experiment by treating the tardigrade as a dielectric cube.

The experimental setup consisted of two superconducting capacitors, which when cooled can exist in a superposition of states called a qubit. They placed the tardigrade between the capacitor plates of one qubit so that it became an integral part of the capacitor. The team was then able to measure the effect of the tardigrade on the qubit’s properties.

How a Tardigrade "Micro Animal" Became Quantum Entangled with Superconducting Qubit, The Physics AriXiv Blog, Discovery Magazine

New state of matter: The team observed electron quadruplets in this iron-based superconductor material, seen mounted for experimental measurements. (Courtesy: Vadim Grinenko, Federico Caglieris)

Topics: Condensed Matter Physics, Solid-State Physics, Superconductors

Note: I gave my research proposal last Friday. I have been answering some concerns about my proposal for the committee. I followed the outline sent to me by my advisor. I hope I've answered them sufficiently. I will post today and tomorrow; next week on Monday, Wednesday, and Friday. I tutor Calculus. For a person finished with classes, I'm extremely busy.

Cool a material below its superconducting transition temperature and you’d expect it to start conducting electricity without resistance and expelling magnetic fields. But an international group of physicists has found that a certain kind of iron-based material doped with negative charges does the opposite at around the same temperature – producing spontaneous magnetic fields and retaining resistance when chilled. The researchers say that the results point to a new state of matter in which electrons flow in correlated groups of four, rather than two.

According to the Bardeen-Cooper-Schrieffer (BCS) theory, superconductivity occurs when electrons get together to form what is known as Cooper pairs. Whereas in a vacuum two electrons would repel each other, when moving through the crystal lattice of a superconducting material, one of these particles shifts the positions of surrounding atoms to leave a small region of positive charge. This attracts the second electron to create the pair.

The creation of many such pairs yields a collective condensate, which results in frictionless electron flow. This occurs below a certain temperature – the superconducting transition temperature (T_c) – at which point atoms lack the thermal energy to break up the pairs.

Superconductor reveals new state of matter involving pairs of Cooper pairs, Edwin Cartlidge, Physics World

Image source: CERN - accelerating science

Topics: CERN, Condensed Matter Physics, Entanglement, Lasers, Quantum Mechanics

Much of modern experimental physics relies on a counterintuitive principle: Under the right circumstances, zapping matter with a laser doesn’t inject energy into the system; rather, it sucks the energy out. By cooling the system to a fraction of a degree above absolute zero, one can observe quantum effects that are otherwise invisible.

Laser cooling works like a charm, but only when a system’s ladder of quantum states is just right. Atoms of alkali metals and a few other elements are ideal. Molecules, with their multitudes of energy levels, pose a much greater challenge. And fundamental particles such as protons, which lack internal states altogether, can’t be laser-cooled at all.

Nevertheless, there’s a lot of interest in experimenting on protons at low temperature—in particular, precisely testing how their mass, magnetic moment, and other properties compare with those of antiprotons. Toward that end, the Baryon Antibaryon Symmetry Experiment (BASE) collaboration has now demonstrated a method for using a cloud of laser-cooled beryllium ions to sympathetically cool a single proton, even when the proton and ions are too distant to directly interact.

A superconducting circuit is a cooling teleporter, Johanna L. Miller, Physics Today

Quasiparticles in motion: illustration of ghost polaritons in a calcite crystal being “launched” to record distances by a gold microdisk. (Courtesy: HUST)

Topics: Condensed Matter Physics, Modern Physics, Quantum Mechanics

The existence of ghost hyperbolic surface polaritons has been demonstrated by an international collaboration including researchers in China and the US. Based at Huazhong University of Science and Technology (HUST), National University of Singapore (NUS), National Center for Nanoscience and Technology (NCNST), and the City University of New York (CUNY), the team showed that the polariton – a hybrid light-matter quasiparticle – has a record-breaking propagation distance of three times its photon wavelength. This ghost polariton is an exciting discovery that has applications in sub-wavelength, low-loss imaging, sensing, and information transfer. The full study is described in Nature.

Previously, hyperbolic polaritons, which arise from the strong coupling of electromagnetic radiation to lattice vibrations (phonons) in anisotropic crystals, had only been observed in two forms: bulk polaritons and surface polaritons. Bulk, volume-confined, hyperbolic polaritons (v-HPs) have a real out-of-plane wavevector and hence can propagate within the material supporting them. Surface-confined hyperbolic polaritons (s-HPs), however, have an entirely imaginary out-of-plane wavevector, and so decay exponentially away from the crystal surface, a property called evanescence. The hyperbolic dispersion of these polaritons is the result of the crystal’s dielectric anisotropy, which results in hyperbolic isofrequency contours in k-space (momentum space) and concave wavefronts in real space.

Most studies on v-HPs and s-HPs have been performed in thin layers of van der Waals crystals. These crystals comprise stacks of covalently bound 2D layers that are held together by weak van der Waals forces. However, in such crystal layers, there is no control over the optical axis. This is the direction in which propagating light experiences no birefringence and it is typically aligned with the layers.

Ghost surface polaritons seen for the first time, Kirsty McGhee, Physics World

This simulation shows how a fracton-filled material would be expected to scatter a beam of neutrons.
H. Yan et al., Physical Review Letters

Topics: Condensed Matter Physics, Quantum Mechanics, Theoretical Physics

Your desk is made up of individual, distinct atoms, but from far away its surface appears smooth. This simple idea is at the core of all our models of the physical world. We can describe what’s happening overall without getting bogged down in the complicated interactions between every atom and electron.

So when a new theoretical state of matter was discovered whose microscopic features stubbornly persist at all scales, many physicists refused to believe in its existence.

“When I first heard about fractons, I said there’s no way this could be true because it completely defies my prejudice of how systems behave,” said Nathan Seiberg, a theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey. “But I was wrong. I realized I had been living in denial.”

The theoretical possibility of fractons surprised physicists in 2011. Recently, these strange states of matter have been leading physicists toward new theoretical frameworks that could help them tackle some of the grittiest problems in fundamental physics.

Fractons are quasiparticles — particle-like entities that emerge out of complicated interactions between many elementary particles inside a material. But fractons are bizarre even compared to other exotic quasiparticles because they are totally immobile or able to move only in a limited way. There’s nothing in their environment that stops fractons from moving; rather it’s an inherent property of theirs. It means fractons’ microscopic structure influences their behavior over long distances.

“That’s totally shocking. For me it is the weirdest phase of matter,” said Xie Chen, a condensed matter theorist at the California Institute of Technology.

The ‘Weirdest’ Matter, Made of Partial Particles, Defies Description, Thomas Lewton, Quanta Magazine

The normalized resistance under magnetic fields and anisotropic upper critical magnetic fields of the CsV₃Sb₅ single crystal. Credit: Chinese Physics Letters

Topics: Condensed Matter Physics, Materials Science, Superconductors

Researchers at the Chinese Academy of Sciences have found evidence for an unusual superconducting state in CsV₃Sb₅, a so-called Kagome metal that exhibits exotic electronic properties. The finding could shed new light on how superconductivity emerges in materials where phenomena such as frustrated magnetism and intertwined orders play a major role.

Kagome metals are named after a traditional Japanese basket-weaving technique that produces a lattice of interlaced symmetrical triangles. Physicists are interested in this configuration (known as a Kagome pattern) because when the atoms of metal or other conductors are arranged in this fashion, their electrons behave in unusual ways.

An example is [frustrated] magnetism, which occurs when electrons are “not happy to live together”, observes Ludovic Jaubert, a condensed-matter physicist at the University of Bordeaux in France who was not involved in the present work. In frustrated materials, not all interactions between electron spins can be satisfied at the same time, which prevents the spins from ordering themselves on long-length scales. This failure has significant consequences for the material’s properties: if water behaved like this, for example, it would never freeze.

Unusual superconductivity appears in a Kagome metal, Isabelle Dumé, Physics World