An international group of physicists led by the University of Arkansas has created an artificial material with a structure comparable to graphene.

“We’ve basically created the first artificial graphene-like structure with transition metal atoms in place of carbon atoms,” says Jak Chakhalian, professor of physics and director of the Artificial Quantum Materials Laboratory.

In 2014, Chakhalian was selected as a quantum materials investigator for the Gordon and Betty Moore Foundation. His selection came with a $1.8 million grant, a portion of which funded the study,

Graphene, discovered in 2001, is a one-atom-thick sheet of graphite. Graphene transistors are predicted to be substantially faster and more heat tolerant than today’s silicon transistors and may result in more efficient computers and the next-generation of flexible electronics. Its discoverers were awarded the Nobel Prize in physics in 2010.

The University of Arkansas -led group published its findings this week in Physical Review Letters, the journal of the American Physical Society, in a paper titled “Mott Electrons in an Artificial Graphene-like Crystal of Rare Earth Nickelate.”

“This discovery gives us the ability to create graphene-like structures for many other elements,” says Srimanta Middey, a postdoctoral research associate at the University of Arkansas who led the study.

The research group also included postdoctoral research associates Michael Kareev and Yanwei Cao, doctoral student Xiaoran Liu, and recent doctoral graduate Derek Meyers, now at Brookhaven National Laboratory.

Additional members of the group were David Doennig of the University of Munich, Rossitza Pentcheva of the University of Duisburg-Essen in Germany, Zhenzhong Yang, Jinan Shi, and Lin Gu of the Chinese Academy of Sciences; and John W. Freeland and Phillip Ryan of the Advanced Photon Source at Argonne National Laboratory near Chicago.

The research was also partially funded by the Chinese Academy of Sciences.

The abstract of their report reads: Deterministic control over the periodic geometrical arrangement of the constituent atoms is the backbone of the material properties, which, along with the interactions, define the electronic and magnetic ground state. Following this notion, a bilayer of a prototypical rare-earth nickelate, NdNiO₃, combined with a dielectric spacer, LaAlO₃, has been layered along the pseudocubic [111] direction. The resulting artificial graphenelike Mott crystal with magnetic 3D electrons has antiferromagnetic correlations. In addition, a combination of resonant X-ray linear dichroism measurements and ab initio calculations reveal the presence of an ordered orbital pattern, which is unattainable in either bulk nickelates or nickelate based heterostructures grown along the [001] direction. These findings highlight another promising venue towards designing new quantum many-body states by virtue of geometrical engineering. 

Release Date: February 2, 2016
Source: University of Arkansas