BLOGS

A new study by KTH Royal Institute of Technology and Stanford University revises of our understanding of quantum vortices in superconductors. Pictured an artist’s depiction of quantum vortices. Credit: Greg Stewart, SLAC National Accelerator Laboratory

Topics: Modern Physics, Quantum Mechanics, Research, Superconductors

Within superconductors, little tornadoes of electrons, known as quantum vortices, can occur, which have important implications in superconducting applications such as quantum sensors. Now a new kind of superconducting vortex has been found, an international team of researchers reports.

Egor Babaev, professor at KTH Royal Institute of Technology in Stockholm, says the study revises the prevailing understanding of how electronic flow can occur in superconductors, based on work about quantum vortices that was recognized in the 2003 Nobel Prize award. The researchers at KTH, together with researchers from Stanford University, TD Lee Institute in Shanghai, and AIST in Tsukuba, discovered that the magnetic flux produced by vortices in a superconductor can be divided up into a wider range of values than thought.

That represents a new insight into the fundamentals of superconductivity and also potentially can be applied in superconducting electronics.

A vortex of magnetic flux happens when an external magnetic field is applied to a superconductor. The magnetic field penetrates the superconductor in the form of quantized magnetic flux tubes, which form vortices. Babaev says that originally research held that quantum vortices pass through superconductors each carrying one quantum of magnetic flux. But arbitrary fractions of quantum flux were not a possibility entertained in earlier theories of superconductivity.

Using the Superconducting Quantum Interference Device (SQUID) at Stanford University Babaev's co-authors, research scientist Yusuke Iguchi and Professor Kathryn A. Moler, showed at a microscopic level that quantum vortices can exist in a single electronic band. The team was able to create and move around these fractional quantum vortices, Moler says.

"Professor Babaev has been telling me for years that we could see something like this, but I didn't believe it until Dr. Iguchi actually saw it and conducted a number of detailed checks," she says.

Tiny quantum electronic vortexes can circulate in superconductors in ways not seen before, KTH Royal Institute of Technology, 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

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

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

A diagram showing different states of matter as a function of temperature, T, and interaction strength, U (normalized to the amplitude, t, of electrons hopping between sites). Strange metals emerge in a regime separating a metallic spin glass and a Fermi liquid. P. Cha et al./Proceedings of the National Academy of Sciences 2020

Topics: Black Holes, Modern Physics, Quantum Mechanics, Superconductors, Theoretical Physics

Even by the standards of quantum physicists, strange metals are just plain odd. The materials are related to high-temperature superconductors and have surprising connections to the properties of black holes. Electrons in strange metals dissipate energy as fast as they’re allowed to under the laws of quantum mechanics, and the electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.

Generating a theoretical understanding of strange metals is one of the biggest challenges in condensed matter physics. Now, using cutting-edge computational techniques, researchers from the Flatiron Institute in New York City and Cornell University have solved the first robust theoretical model of strange metals. The work reveals that strange metals are a new state of matter, the researchers report July 22 in the Proceedings of the National Academy of Sciences.

“The fact that we call them strange metals should tell you how well we understand them,” says study co-author Olivier Parcollet, a senior research scientist at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ). “Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics.”

Quantum Physicists Crack Mystery of ‘Strange Metals,’ a New State of Matter, Thomas Sumner, Simon Foundation

Image source: link below

Topics: Atomic Physics, Magnetism, Superconductors

Web Elements: Uranium Tritelluride

Exotic superconducting state lurks at an astonishingly high magnetic field
Johanna L. Miller, Physics Today

Under pressure: calculated structure of lithium magnesium hydride. Lithium atoms appear in green, magnesium in blue and hydrogen in red. (Courtesy: Ying Sun et al/Phys. Rev. Lett.)

Topics: Chemistry, Materials Science, Nanotechnology, Superconductors

Superconductivity at the boiling temperature of water is possible, say physicists
Hamish Johnston, Physics World

Superconductors' never-ending flow of electrical current could provide new options for energy storage and superefficient electrical transmission and generation. But the signature zero electrical resistance of superconductors is reached only below a certain critical temperature and is very expensive to achieve. Physicists in Serbia believe they've found a way to manipulate superthin, waferlike monolayers of superconductors, thus changing the material's properties to create new artificial materials for future devices. This image shows a liquid phase graphene film deposited on PET substrate. Credit: Graphene Laboratory, University of Belgrade

Topics: Applied Physics, Superconductors, Thin Films

Strain enables new applications of 2-D materials, Phys.org