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 Using fine-tuning for record-breaking performance
14.11.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

nachricht Materials scientist creates fabric alternative to batteries for wearable devices
12.11.2018 | University of Massachusetts at Amherst

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

NIH scientists illuminate causes of hepatitis b virus-associated acute liver failure

14.11.2018 | Life Sciences

The unintended consequences of dams and reservoirs

14.11.2018 | Earth Sciences

NIH scientists combine technologies to view the retina in unprecedented detail

14.11.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>