Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mapping the behavior of charges in correlated spin-orbit coupled materials

10.03.2014

Electronic disruption prods Mott insulator's conversion to metallic state

In a relatively recently discovered class of materials, known as spin-orbit Mott insulators, theorists have predicted the emergence of new properties at points just beyond the insulating state, when electronic manipulation can transform these compounds into conducting metals.


Images obtained through scanning tunneling spectroscopy show the transformation of a compound of strontium, iridium and oxygen -- part of a mysterious class of materials known as spin-orbit Mott insulators. By introducing charge carriers within the compound by replacing 40 percent of the iridium ions with ruthenium, researchers from Boston College were able to reveal the microscopic mechanisms that transform these insulators into a metallic state. The images reveal ruthenium effectively created features within the compound that resembled minute metallic puddles. As the amount of additional ruthenium was increased, the puddles 'percolate,' coalescing to form a metal across which charges freely flow.

Credit: Nature Communications

A better understanding of electrons near this transition, theorists have predicted, could allow these new Mott insulators to pave the way to discoveries in superconductivity, new topological phases of matter, and new forms of unusual magnetism.

What scientists have lacked is experimental evidence that reveals the microscopic mechanisms that actually drive one of these spin-orbit Mott insulators to become a metal.

Now a team of physicists at Boston College report in Nature Communications that they manipulated a compound of strontium, iridium and oxygen – Sr3Ir207 – with a substitution of ruthenium metal ions, successfully driving the material into the metallic regime, and mapping this previously uncharted transformation as it took place, giving scientists a unique view into the workings of these insulators.

Spin-orbit Mott insulators are so named because of their complex electronic properties. Within these novel materials, there is a repulsive interaction between electrons that tends to drive the electrons to a stand still. This tendency is bolstered by the lowering of the electron's energy via a strong interaction between the electron's magnetic field and its orbital motion around the nucleus.

This delicate interplay between repulsive action, known as Coulomb interaction, and the coupling between electrons' spin and orbital motion has allowed scientists to define this class of materials as spin-orbit Mott insulators.

Boston College Assistant Professor of Physics Stephen D. Wilson said the team succeeded in driving the insulator-to-metal transformation by replacing 40 percent of the iridium ions with ruthenium, thereby creating a metal alloy. That event introduced charge carriers, which have proven successful in destabilizing the so-called Mott phase in the transformation of compounds in this class of insulators.

Scanning tunneling microscopy revealed ruthenium effectively created features within the compound that resembled minute metallic puddles, said Wilson, one of the lead researchers on the project. As the amount of additional ruthenium was increased, the puddles began to "percolate," coalescing to form a metal across which charges freely flow, he added.

"The addition of ruthenium introduces charge carriers, but at a low ratio of ruthenium to iridium they simply stay put in these little metallic puddles, which are symptoms of strong correlated electrons," Wilson said. "These electrons are stable and wouldn't move much. But when we stepped up the disruption by increasing the amount of ruthenium, the puddles moved together and achieved a metallic state."

The behavior in this particular compound parallels what researchers have seen in Mott insulators that play host to such phenomenon as high temperature superconductivity, said Wilson, who will discuss his research at the upcoming annual meeting of the American Physical Society.

By pinpointing exactly where this transformation takes place, the team's findings should help to lay the groundwork in the scientific search for new electronic phases within spin-orbit Mott insulators, said Wilson, who co-authored the report with his Boston College Department of Physics colleagues Professor Vidya Madhavan, Professor Ziqiang Wang, and Assoc. Prof. Fr. Cyril P. Opeil, SJ.

###

BC graduate students Chetan Dhital, the lead author of the paper, Tom Hogan, Wenwen Zhou, Xiang Chen, Zhensong Ren, Mani Pokharel, and M. Heine also contributed to the project. Scientists at the Oak Ridge National Laboratory, the U.S. National Institute of Standards and Technology and the Canadian Center for Neutron Research also collaborated on the research.

Ed Hayward | EurekAlert!
Further information:
http://www.bc.edu

Further reports about: Physics behavior carriers electrons insulators ions iridium materials metallic properties puddles

More articles from Materials Sciences:

nachricht Serendipity uncovers borophene's potential
23.02.2017 | Northwestern University

nachricht Switched-on DNA
20.02.2017 | Arizona State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>