Scientists finally find superconductivity in…

Scientists finally find superconductivity in place they have been looking for decades

Researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory say they have found the first, long-sought proof that a decades-old scientific model of material behavior can be used to simulate and understand high-temperature superconductivity ­- an important step toward producing and controlling this puzzling phenomenon at will.

The simulations they ran, published in Science today, suggest that researchers might be able to toggle superconductivity on and off in copper-based materials called cuprates by tweaking their chemistry so electrons hop from atom to atom in a particular pattern—as if hopping to the atom diagonally across the street rather than to the one next door.

“The big thing you want to know is how to make superconductors operate at higher temperatures and how to make superconductivity more robust,” said study co-author Thomas Devereaux, director of the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC. “It’s about finding the knobs you can turn to tip the balance in your favor.”

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Scientists couple magnetization to supercond…

Scientists couple magnetization to superconductivity for quantum discoveries

Quantum computing promises to revolutionize the ways in which scientists can process and manipulate information. The physical and material underpinnings for quantum technologies are still being explored, and researchers continue to look for new ways in which information can be manipulated and exchanged at the quantum level.

In a recent study, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have created a miniaturized chip-based superconducting circuit that couples quantum waves of magnetic spins called magnons to photons of equivalent energy. Through the development of this “on chip” approach that marries magnetism and superconductivity for manipulation of quantum information, this fundamental discovery could help to lay the foundation for future advancements in quantum computing.

Magnons emerge in magnetically ordered systems as excitations within a magnetic material that cause an oscillation of the magnetization directions at each atom in the material—a phenomenon called a spin wave. “You can think of it like having an array of compass needles that are all magnetically linked together,” said Argonne materials scientist Valentine Novosad, an author of the study. “If you kick one in a particular direction, it will cause a wave that propagates through the rest.”

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For superconductors, discovery comes from di…

For superconductors, discovery comes from disorder

Discovered more than 100 years ago, superconductivity continues to captivate scientists who seek to develop components for highly efficient energy transmission, ultrafast electronics or quantum bits for next-generation computation. However, determining what causes substances to become—or stop being—superconductors remains a central question in finding new candidates for this special class of materials.

In potential superconductors, there may be several ways electrons can arrange themselves. Some of these reinforce the superconducting effect, while others inhibit it. In a new study, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have explained the ways in which two such arrangements compete with each other and ultimately affect the temperature at which a material becomes superconducting.

In the superconducting state, electrons join together into so-called Cooper pairs, in which the motion of electrons is correlated; at each moment, the velocities of the electrons participating in a given pair are opposite. Ultimately, the motion of all electrons is coupled—no single electron can do its own thing—which leads to the lossless flow of electricity: superconductivity.

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Unraveling the stripe order mystery

Unraveling the stripe order mystery

One of the greatest mysteries in condensed matter physics is the exact relationship between charge order and superconductivity in cuprate superconductors. In superconductors, electrons move freely through the material—there is zero resistance when it’s cooled below its critical temperature. However, the cuprates simultaneously exhibit superconductivity and charge order in patterns of alternating stripes. This is paradoxical in that charge order describes areas of confined electrons. How can superconductivity and charge order coexist?

Now researchers at the University of Illinois at Urbana-Champaign, collaborating with scientists at the SLAC National Accelerator Laboratory, have shed new light on how these disparate states can exist adjacent to one another. Illinois Physics post-doctoral researcher Matteo Mitrano, Professor Peter Abbamonte, and their team applied a new X-ray scattering technique, time-resolved resonant soft X-ray scattering, taking advantage of the state-of-the-art equipment at SLAC. This method enabled the scientists to probe the striped charge order phase with an unprecedented energy resolution. This is the first time this has been done at an energy scale relevant to superconductivity.

The scientists measured the fluctuations of charge order in a prototypical copper-oxide superconductor, La2-xBaxCuO4 (LBCO) and found the fluctuations had an energy that matched the material’s superconducting critical temperature, implying that superconductivity in this material—and by extrapolation, in the cuprates—may be mediated by charge-order fluctuations.

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Similarities in the insulating states of twi…

Similarities in the insulating states of twisted bilayer graphene and cuprates

In recent decades, enormous research efforts have been expended on the exploration and explanation of high-temperature (high-Tc) superconductors, a class of materials exhibiting zero resistance at particularly high temperatures. Now a team of scientists from the United States, Germany and Japan explains in Nature how the electronic structure in twisted bilayer graphene influences the emergence of the insulating state in these systems, which is the precursor to superconductivity in high-Tc materials.

Finding a material which superconducts at room temperature would lead to a technological revolution, alleviate the energy crisis (as nowadays most energy is lost on the way from generation to usage) and boost computing performance to an entirely new level. However, despite the progress made in understanding these systems, a full theoretical description is still elusive, leaving our search for room temperature superconductivity mainly serendipitous.

In a major scientific breakthrough in 2018, twisted bilayer graphene (TBLG) was shown to exhibit phases of matter akin to those of a certain class of high-Tc superconducting materials—the so-called high-Tc cuprates. This represents a novel inroad via a much cleaner and more controllable experimental setup.

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From Japanese basket weaving art to nanotech…

From Japanese basket weaving art to nanotechnology with ion beams

The properties of high-temperature superconductors can be tailored by the introduction of artificial defects. An international research team around physicist Wolfgang Lang at the University of Vienna has succeeded in producing the world’s densest complex nano arrays for anchoring flux quanta, the fluxons. This was achieved by irradiating the superconductor with a helium-ion microscope at the University of Tübingen, a technology that has only recently become available. The researchers were inspired by a traditional Japanese basket weaving art. The results have been published recently in ACS Applied Nano Materials, a journal of the renowned American Chemical Society.

Superconductors can carry electricity without loss if they are cooled below a certain critical temperature. However, pure superconductors are not suitable for most technical applications, but only after controlled introduction of defects. Mostly, these are randomly distributed, but nowadays the tailored periodic arrangement of such defects becomes more and more important.

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Experiments explore the mysteries of ‘…

Experiments explore the mysteries of ‘magic’ angle superconductors

In spring 2018, the surprising discovery of superconductivity in a new material set the scientific community abuzz. Built by layering one carbon sheet atop another and twisting the top one at a “magic” angle, the material enabled electrons to flow without resistance, a trait that could dramatically boost energy efficient power transmission and usher in a host of new technologies.

Now, new experiments conducted at Princeton give hints at how this material—known as magic-angle twisted graphene—gives rise to superconductivity. In this week’s issue of the journal Nature, Princeton researchers provide firm evidence that the superconducting behavior arises from strong interactions between electrons, yielding insights into the rules that electrons follow when superconductivity emerges.

“This is one of the hottest topics in physics,” said Ali Yazdani, the Class of 1909 Professor of Physics and senior author of the study. “This is a material that is incredibly simple, just two sheets of carbon that you stick one on top of the other, and it shows superconductivity.”

Exactly how superconductivity arises is a mystery that laboratories around the world are racing to solve. The field even has a name, “twistronics.”

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A graphene superconductor that plays more than…

A graphene superconductor that plays more than one tune: Researchers at Berkeley Lab have developed a tiny toolkit for scientists to study exotic quantum physics

Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a graphene device that’s thinner than a human hair but has a depth of special traits. It easily switches from a superconducting material that conducts electricity without losing any energy, to an insulator that resists the flow of electric current, and back again to a superconductor – all with a simple flip of a switch. Their findings were reported today in the journal Nature.

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“Usually, when someone wants to study how electrons interact with each other in a superconducting quantum phase versus an insulating phase, they would need to look at different materials. With our system, you can study both the superconductivity phase and the insulating phase in one place,” said Guorui Chen, the study’s lead author and a postdoctoral researcher in the lab of Feng Wang, who led the study. Wang, a faculty scientist in Berkeley Lab’s Materials Sciences Division, is also a UC Berkeley physics professor.

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Alternative material for superconducting rad…

Alternative material for superconducting radio-frequency cavity

In modern synchrotron sources and free-electron lasers, superconducting radio-frequency cavity resonators are able to supply electron bunches with extremely high energy. These resonators are currently constructed of pure niobium. Now an international collaboration has investigated the potential advantages a niobium-tin coating might offer in comparison to pure niobium.

At present, niobium is the material of choice for constructing superconducting radio-frequency cavity resonators. These will be used in projects at the HZB such as bERLinPro and BESSY-VSR, but also for free-electron lasers such as the XFEL and LCLS-II. However, a coating of niobium-tin (Nb3Sn) could lead to considerable improvements.

Superconducting radio-frequency cavity resonators made of niobium must be operated at 2 Kelvin (-271 degrees Celsius), which requires expensive and complicated cryogenic engineering. In contrast, a coating of Nb3Sn might make it possible to operate resonators at 4 Kelvin instead of 2 Kelvin and possibly withstand higher electromagnetic fields without the superconductivity collapsing. In the future, this could save millions of euros in construction and electricity costs for large accelerators, as the cost of cooling would be substantially lower.

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Pairing ‘glue’ for electrons in …

Pairing ‘glue’ for electrons in iron-based high-temp superconductors studied

Newly published research from a team of scientists led by the U.S. Department of Energy’s Ames Laboratory sheds more light on the nature of high-temperature iron-based superconductivity.

Current theories suggest that magnetic fluctuations play a very significant role in determining superconducting properties and even act as a “pairing glue” in iron-based superconductors.

“A metal becomes a superconductor when normal electrons form what physicists call Cooper pairs. The interactions responsible for this binding are often referred to as ‘pairing glue.’ Determining the nature of this glue is the key to understanding, optimizing and controlling superconducting materials,” said Ruslan Prozorov, an Ames Laboratory physicist who is an expert in superconductivity and magnetism.

The scientists, from Ames Laboratory, Nanjing University, University of Minnesota, and L’École Polytechnique, focused their attention on high quality single crystal samples of one widely studied family of iron-arsenide high-temperature superconductors. They sought an experimental approach to systematically disrupt the magnetic, electronic and superconducting ordered states; while keeping the magnetic field, temperature, and pressure unchanged.

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