Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Strange electrons break the crystal symmetry of high-temperature superconductors: Brookhaven Lab scientists discover spontaneous voltage perpendicular to applied current that may help unravel the mystery of high-temperature superconductors

Brookhaven Lab scientists (from left) Ivan Bozovic, Xi He, Jie Wu, and Anthony Bollinger with the atomic layer-by-layer molecular beam epitaxy system used to synthesize the superconducting cuprate samples.
CREDIT
Brookhaven National Laboratory
Brookhaven Lab scientists (from left) Ivan Bozovic, Xi He, Jie Wu, and Anthony Bollinger with the atomic layer-by-layer molecular beam epitaxy system used to synthesize the superconducting cuprate samples. CREDIT Brookhaven National Laboratory

Abstract:
The perfect performance of superconductors could revolutionize everything from grid-scale power infrastructure to consumer electronics, if only they could be coerced into operating above frigid temperatures. Even so-called high-temperature superconductors (HTS) must be chilled to hundreds of degrees Fahrenheit below zero.

Strange electrons break the crystal symmetry of high-temperature superconductors: Brookhaven Lab scientists discover spontaneous voltage perpendicular to applied current that may help unravel the mystery of high-temperature superconductors

Upton, NY | Posted on July 27th, 2017

Now, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Yale University have discovered new, surprising behavior by electrons in a HTS material. The results, published July 27 in the journal Nature, describe the symmetry-breaking flow of electrons through copper-oxide (cuprate) superconductors. The behavior may be linked to the ever-elusive mechanism behind HTS.

"Our discovery challenges a cornerstone of condensed matter physics," said lead author and Brookhaven Lab physicist Jie Wu. "These electrons seem to spontaneously 'choose' their own paths through the material -- a phenomenon in direct opposition to expectations."

Off-road electrons

In simple metals, electrons move evenly and without directional preference -- think of a liquid spreading out on a surface. The HTS materials in this study are layered with four-fold rotational symmetry of the crystal structure. Electric current is expected to flow uniformly parallel to these layers -- but this is not what the Brookhaven group observed.

"I'm from the Midwest, where miles of farmland separate the cities," said Brookhaven physicist and study coauthor Anthony Bollinger. "The country roads between the cities are largely laid out like a grid going north-to-south and east-to-west. You expect cars to follow the grid, which is tailor-made for them. This symmetry breaking is as if everyone decided to leave the paved roads and drive straight across farmers' fields."

In another twist, the symmetry-breaking voltage persisted up to room temperature and across the whole range of chemical compositions the scientists examined.

"The electrons somehow coordinate their movement through the material, even after the superconductivity fails," said Wu.

Strong electron-electron interactions may help explain the preferential direction of current flow. In turn, these intrinsic electronic quirks may share a relationship with HTS phenomena and offer a hint to decoding its unknown mechanism.

Seeking atomic perfection

Unlike well-understood classical superconductivity, HTS has puzzled scientists for more than three decades. Now, advanced techniques are offering unprecedented insights.

"The most difficult part of the whole work -- and what helps set us apart -- was the meticulous material synthesis," said study coauthor Xi He.

This work was a part of a larger project that took 12 years and encompassed the synthesis and study of more than 2,000 films of lanthanum-strontium-copper-oxide superconductors.

"This scale of research is well-suited to a national laboratory environment," said Ivan Bozovic, who leads the Brookhaven group behind the effort.

They use a technique called molecular beam epitaxy (MBE) to assemble complex oxides one atomic layer at a time. To ensure structural perfection, the scientists characterize the materials in real time with electron diffraction, where an electron beam strikes the sample and sensitive detectors measure precisely how it scatters.

"The material itself is our foundation, and it must be as flawless as possible to guarantee that the observed properties are intrinsic," Bozovic said. "Moreover, by virtue of our 'digital' synthesis, we engineer the films at the atomic-layer level, and optimize them for different studies."

Swimming against the current

The first major result of this comprehensive study by the MBE group at Brookhaven was published in Nature last year. It demonstrated that the superconducting state in copper-oxide materials is quite unusual, challenging the standard understanding.

That finding suggested that the so-called "normal" metallic state, which forms above the critical temperature threshold at which superconductivity breaks down, might also be extraordinary. Looking carefully, the scientists observed that as external current flowed through the samples, a spontaneous voltage unexpectedly emerged perpendicular to that current.

"We first observed this bizarre voltage over a decade ago, but we and others discounted that as some kind of error," Bollinger said. "But then it showed up again, and again, and again -- under increasingly controlled conditions -- and we ran out of ways to explain it away. When we finally dove in, the results exceeded our expectations."

To pin down the origin of the phenomenon, the scientists fabricated and measured thousands of devices patterned out of the HTS films. They studied how this spontaneous voltage depends on the current direction, temperature, and the chemical composition (the level of doping by strontium, which controls the electron density). They also varied the type and the crystal structure of the substrates on which the HTS films are grown, and even how the substrates are polished.

These meticulous studies showed beyond doubt that the effect is intrinsic to the HTS material itself, and that its origin is purely electronic.

At the molecular level, common liquids look the same in every direction. Some, however, are comprised of rod-like molecules, which tend to align in one preferred direction. Such materials are called liquid crystals -- they polarize light and are widely used in displays. While electrons in common metals behave as a liquid, in cuprates they behave as an electronic liquid crystal.

"We need to understand how this electron behavior fits into the HTS puzzle as a whole," He said. "This study gives us new ideas to pursue and ways to tackle what may be the biggest mystery in condensed matter physics. I'm excited to see where this research takes us."

###

Authors Bozovic and He share affiliation with Brookhaven Lab and Yale University.

The research was funded by DOE's Office of Science.

####

About Brookhaven National Laboratory
Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

For more information, please click here

Contacts:
Ariana Tantillo

631-344-2347

Copyright © Brookhaven National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Superconductivity

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

'Sudden death' of quantum fluctuations defies current theories of superconductivity: Study challenges the conventional wisdom of superconducting quantum transitions January 12th, 2024

Laboratories

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Catalytic combo converts CO2 to solid carbon nanofibers: Tandem electrocatalytic-thermocatalytic conversion could help offset emissions of potent greenhouse gas by locking carbon away in a useful material January 12th, 2024

Govt.-Legislation/Regulation/Funding/Policy

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Possible Futures

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Chip Technology

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Discoveries

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

High-tech 'paint' could spare patients repeated surgeries March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Announcements

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Energy

Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024

Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023

Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023

The efficient perovskite cells with a structured anti-reflective layer – another step towards commercialization on a wider scale October 6th, 2023

Research partnerships

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

'Sudden death' of quantum fluctuations defies current theories of superconductivity: Study challenges the conventional wisdom of superconducting quantum transitions January 12th, 2024

Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project