Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Research reveals novel quantum state in strange insulating materials

When a Mott insulator with strong spin-order coupling is cooled, its atomic lattice distorts, breaking its cubic symmetry. That distortion drives a unique form of layered magnetism within the materials.
CREDIT
Mitrovi? lab / Brown University
When a Mott insulator with strong spin-order coupling is cooled, its atomic lattice distorts, breaking its cubic symmetry. That distortion drives a unique form of layered magnetism within the materials. CREDIT Mitrovi? lab / Brown University

Abstract:
Researchers from Brown University have shown experimentally how a unique form of magnetism arises in an odd class of materials called Mott insulators. The findings are a step toward a better understanding the quantum states of these materials, which have generated much interest among scientists in recent years.

Research reveals novel quantum state in strange insulating materials

Providence, RI | Posted on February 14th, 2017

The study, published in Nature Communications, helps to confirm novel theoretical work that attempts to explain how electrons behave in these strange materials. The work was done in collaboration with scientists at Stanford University and the National High Magnetic Field Laboratory.

"We found that the theory holds up well," said Vesna Mitrović, an associate professor of physics at Brown who led the work. "It shows that this new theory, based on quantum models involving complicated electron spin interactions, is a good start to understanding magnetism in strongly interacting materials."

Mott insulators are materials that should be conductors according to traditional theories of electrical conductivity, but act as insulators nonetheless. The insulating state arises because electrons in these materials are strongly correlated and repel each other. That dynamic creates a kind of electron traffic jam, preventing the particles from flowing to form a current.

Scientists are hopeful that they can find ways of moving these materials in and out of the Mott insulating state, which would be useful in developing new kinds of functional devices. It's also been shown that by introducing impurities into their structure, some Mott insulators become high-temperature superconductors--materials that can conduct electricity without resistance at temperatures well above those normally required for superconductivity.

Despite the promise of these materials, scientists still don't fully understand how they work. A full description of electron states in these materials has been elusive. On the most fundamental level, each individual electron is characterized by its charge and spin, its tiny magnetic moment that points either up or down. It's difficult to predict electron properties in Mott insulators because the states of electrons are so closely correlated with each other--the state of one electron influences the states of its neighbors.

To further complicate matters, many Mott insulators exhibit what is known as spin-orbit coupling, meaning that each electron's spin changes as it orbits an atomic nucleus. Spin-orbit coupling implies that the magnetic moment of electron is affected by its orbiting an atomic nucleus, and therefore the spin of an electron is not well defined. Thus, predicting properties of these materials requires knowledge of interactions between the electrons while the fundamental properties of individual electron depend on their orbital motion.

"When you have these complex interactions plus spin-order coupling, it becomes an incredibly complicated situation to describe theoretically," Mitrović said. "Yet we need such fundamental quantum theory to be able to predict novel quantum properties of complex materials and harness them."

Mitrović's study focused on a strange type of magnetism that arises when Mott insulators with strong spin-orbit coupling are cooled below a critical temperature. Magnetism arises as a result of alignments between electrons spins. But in this case, because the spins are strongly interacting and their values depend on orbital motion, it's not understood how this magnetism arises in these materials.

There was one important theoretical attempt to show what might be happening in these materials on the most fundamental level to bring on this magnetic state. And that's what Mitrović and her colleagues wanted to test.

Mitrović's colleagues at Stanford started by synthesizing and characterizing thermodynamically a Mott insulating material made of barium, sodium, osmium and oxygen, which Mitrović probed using nuclear magnetic resonance. The particular technique the team used enabled them to gather information about the distribution of electron charges in the material and information about electron spin at the same time.

The work showed that as the material is cooled, changes in the distribution of electron charges cause distortion in the material's atomic orbitals and lattice. As the temperature cools further, that distortion drives the magnetism by causing an alignment of electron spins within individual layers of the atomic lattice.

"We were able to determine the exact nature of the orbital charge distortions that precedes the magnetism, as well as the exact spin alignment in this exotic magnetic state." Mitrović said. "In one layer you have spins aligned in one direction, and then in the layers above and below it the spins are aligned in the different direction. That results in weak magnetism over all, despite the strong magnetism within each layer."

The theory Mitrović was investigating predicted exactly this layered magnetism preceded by distortions of charge. As such, the findings help to confirm that the theory is on the right track.

The work is an important step toward understanding and manipulating the properties of this interesting class of materials for real-world applications, Mitrović says. In particular, materials with spin-order coupling are promising for the development of electronic devices that consume less power than ordinary devices.

"If we want to start using these materials in devices, we need to understand how they work fundamentally," Mitrović said. "That way we can tune their properties for what we want them to do. By validating some of the theoretical work on Mott insulators with strong spin-orbit coupling, this work is an important step toward a better understanding."

In a larger sense, the work is a step toward a more comprehensive quantum theory of magnetism.

"Even though magnetism is the longest known quantum phenomena, discovered by the ancient Greeks, a fundamental quantum theory of magnetism remains elusive," Mitrović said. "We designed our work to test a novel theory that attempts to explain how magnetism arises in exotic materials."

###

The work was supported by the National Science Foundation (DMR-0547938 and DMR-1608760) and the Department of Energy. Mitrović's co-authors were Lu Lu, Myeongun Song, Wencong Liu, Arneil Reyes, Phil Kuhns, H. O. Lee and Ian Fisher.

####

For more information, please click here

Contacts:
Kevin Stacey

401-863-3766

Copyright © Brown University

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 printed graphene-like materials with inkjet August 17th, 2017

Candy cane supercapacitor could enable fast charging of mobile phones August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Gold shines through properties of nano biosensors: Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves August 16th, 2017

Physics

Sensing technology takes a quantum leap with RIT photonics research: Office of Naval Research funds levitated optomechanics project August 10th, 2017

'Perfect Liquid' Quark-Gluon Plasma is the Most Vortical Fluid: Swirling soup of matter's fundamental building blocks spins ten billion trillion times faster than the most powerful tornado, setting new record for "vorticity" August 4th, 2017

The first light atomic nucleus with a second face July 20th, 2017

Quantum Physics

Nanocrystalline LEDs: Red, green, yellow, blue ... August 7th, 2017

Ultracold molecules hold promise for quantum computing: New approach yields long-lasting configurations that could provide long-sought “qubit” material July 27th, 2017

Carbon displays quantum effects July 13th, 2017

Superconductivity

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 July 27th, 2017

Iron secrets behind superconductors unlocked July 7th, 2017

Govt.-Legislation/Regulation/Funding/Policy

Researchers printed graphene-like materials with inkjet August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

2-faced 2-D material is a first at Rice: Rice University materials scientists create flat sandwich of sulfur, molybdenum and selenium August 14th, 2017

Engineers pioneer platinum shell formation process – and achieve first-ever observation August 11th, 2017

Possible Futures

Researchers printed graphene-like materials with inkjet August 17th, 2017

Candy cane supercapacitor could enable fast charging of mobile phones August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Gold shines through properties of nano biosensors: Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves August 16th, 2017

Chip Technology

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Two Scientists Receive Grants to Develop New Materials: Chad Mirkin and Monica Olvera de la Cruz recognized by Sherman Fairchild Foundation August 16th, 2017

Surprise discovery in the search for energy efficient information storage August 10th, 2017

GLOBALFOUNDRIES Demonstrates 2.5D High-Bandwidth Memory Solution for Data Center, Networking, and Cloud Applications: Solution leverages 2.5D packaging with low-latency, high-bandwidth memory PHY built on FX-14™ ASIC design system August 9th, 2017

Discoveries

Researchers printed graphene-like materials with inkjet August 17th, 2017

Candy cane supercapacitor could enable fast charging of mobile phones August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Gold shines through properties of nano biosensors: Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves August 16th, 2017

Materials/Metamaterials

Researchers printed graphene-like materials with inkjet August 17th, 2017

Two Scientists Receive Grants to Develop New Materials: Chad Mirkin and Monica Olvera de la Cruz recognized by Sherman Fairchild Foundation August 16th, 2017

Fewer defects from a 2-D approach August 15th, 2017

2-faced 2-D material is a first at Rice: Rice University materials scientists create flat sandwich of sulfur, molybdenum and selenium August 14th, 2017

Announcements

Researchers printed graphene-like materials with inkjet August 17th, 2017

Candy cane supercapacitor could enable fast charging of mobile phones August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Gold shines through properties of nano biosensors: Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves August 16th, 2017

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

Researchers printed graphene-like materials with inkjet August 17th, 2017

Candy cane supercapacitor could enable fast charging of mobile phones August 17th, 2017

Freeze-dried foam soaks up carbon dioxide: Rice University scientists lead effort to make novel 3-D material August 16th, 2017

Gold shines through properties of nano biosensors: Researchers discover that fluorescence in ligand-protected gold nanoclusters is an intrinsic property of the gold particles themselves August 16th, 2017

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



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project