superconductors (5)

Kagome Metal...

kagome.jpg

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

Read more…

Strange Metals...

StrangeMetals-PhaseDiagram.png?auto=format&w=485&q=90

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

Read more…

Uranium Telluride...

media_sizes_full_f1-2.jpg
Image source: link below


Topics: Atomic Physics, Magnetism, Superconductors


Superconductivity and magnetism don’t usually mix. When a superconductor is placed in a magnetic field, it expels the field from its bulk through the Meissner effect; a strong enough field destroys the superconducting state entirely. In the vast majority of superconductors, electrons form spin-singlet pairs, with s– or d-wave symmetry, that are twisted apart by the field. Even the rare p-wave, spin-triplet superconductors (such as strontium ruthenate; see Physics Today, December 2006, page 23) are limited in how strong a magnetic field they can tolerate.
 
Te3U1-12040185.jpg
Web Elements: Uranium Tritelluride

Last year the list of unusual superconductors grew by one, when Nicholas Butch and colleagues at NIST and the University of Maryland discovered spin-triplet superconductivity in uranium telluride, or UTe2. (The paper reporting their results, although submitted in October 2018, wasn’t published until this August; in the intervening time, the discovery was confirmed by a team of researchers at Tohoku University in Japan and Grenoble Alps University in France.)

 

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

Read more…

Boiling Superconductivity...

Hydride.png
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


A material that remains a superconductor when heated to the boiling point of water has been predicted by physicists in China. Hanyu Liu, Yanming Ma and colleagues at Jilin University have calculated that lithium magnesium hydride will superconduct at temperatures as high as 473 K (200 °C).

The catch is that the hydrogen-rich material must be crushed at 250 GPa, which is on par with pressures at the center of the Earth. While such a pressure could be achieved in the lab, it would be very difficult to perform an experiment to verify the prediction. The team’s research could, however, lead to the discovery of more practical high-temperature superconductors.

Superconductors are materials that, when cooled below a critical temperature, will conduct electricity with zero resistance. Most superconductors need to be chilled to very low temperatures, so the holy grail of superconductivity research is to find a substance that will superconduct at room temperature. This would result in lossless electricity transmission and boost technologies that rely on the generation or detection of magnetic fields.

 

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

Read more…
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


Superconductors' never-ending flow of electrical current could provide new options for energy storage and superefficient electrical transmission and generation, to name just a few benefits. But the signature zero electrical resistance of superconductors is reached only below a certain critical temperature, hundreds of degrees Celsius below freezing, and is very expensive to achieve.

Physicists from the University of Belgrade in Serbia believe they've found a way to manipulate superthin, waferlike monolayers of superconductors, such as graphene, a monolayer of carbon, thus changing the material's properties to create new artificial materials for future devices. The findings from the group's theoretical calculations and experimental approaches are published in the Journal of Applied Physics.

"The application of tensile biaxial strain leads to an increase of the critical temperature, implying that achieving high temperature superconductivity becomes easier under strain," said the study's first author from the University of Belgrade's LEX Laboratory, Vladan Celebonovic.

 

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

Read more…