Northern Illinois University

Northern Today

Michel van Veenendaal
Michel van Veenendaal

 

Orbitals really do matter

Scientists discover potential new path
for designing novel nanomaterials

October 22, 2007

by Tom Parisi

NIU physicist Michel van Veenendaal is a member of a team of scientists who have uncovered a potential path for manipulating superconductivity at the atomic scale, opening up a new area of investigation into ways of designing nanoscale superconductors.

The team of scientists, led by Jacques Chakalian of the University of Arkansas, presented its finding recently on the Science Express Web site, published by the journal Science.

The scientists conducted their research at Argonne National Laboratory’s Advanced Photon Source, a facility that produces the most powerful X-ray beams in the Western Hemisphere, allowing scientists to observe behavior of atoms and particles at the quantum level.

The researchers used a novel way to “look” at atomic orbitals, and for the first time directly showed that the orbitals of electrons change substantially when interacting at the interface of a ferromagnetic material and high-temperature superconductor. In bulk quantities, the two phenomena are incompatible.

“An unpredicted reconstruction of electronic orbitals and covalent bonding occurred at the interface of the two materials,” said van Veenendaal, who serves as deputy director of NIU’s Institute of Nanoscience & Engineering Technology.

A theoretical physicist, van Veenendaal performed complex mathematical calculations to describe the phenomenon. Atomic orbitals are the intricately shaped wave functions that the electrons of an atom occupy.

“The orbitals and their occupations are entirely different from what scientists would expect, although the effect only occurs in the layers closest to the surface of the interface,” he added.

Many in the scientific community believed that only electron spin and atomic charge – not atomic orbitals – influence the properties of superconducting nanostructures. The interest in particle spin, in fact, led to the emerging field of spintronics, which looks to develop devices that exploit the up-or-down spin property of electrons.

“Our research seems to indicate that manipulation of electron orbitals also could lead to new properties in nanomaterials,” van Veenendaal said. “Instead of electronics or spintronics, we might someday think in terms of ‘orbitronics.’ ”

The team of scientists worked with synchrotron radiation to examine the interface between a high-temperature superconducting material containing copper oxide and a ferromagnetic material containing manganese oxide.

“The goal is to induce some of the properties from one system into the other, thereby achieving two different quantum phenomena at once,” van Veenendaal said. “Our work provides some hope that this might be achieved on the quantum level.”

The discovery might be a step toward the creation of room-temperature nanoscale superconductors. Superconductivity is the phenomenon of almost perfect conductivity shown by certain substances at temperatures approaching absolute zero.

If the phenomenon could be achieved at or near room temperature, it could lead to a wide array of technological innovations. Once set in motion, an electrical current in a closed loop could flow without resistance in near perpetual motion.

“We’re a long way off from creating room-temperature superconductors, but this does open a new path to investigate,” van Veenendaal said. “Growing these layered structures is already a technical feat unto itself.”

He added that the research points to the success of the joint NIU and Argonne theory program.

In 2002, NIU President John Peters and then-Argonne Director Hermann Grunder signed a memorandum of understanding leading to the creation of an alliance between the two institutions to carry out basic research in nanoscience. The agreement established a long-term research program that includes four joint appointments, of which three are in theory. At the APS, the Theory Group collaborates with experimental groups at several beam lines.

“This clearly demonstrates the advantages of joint programs which benefit Argonne, NIU and other universities,” van Veenendaal said. “Without this joint program, there would be no theory support at the Advanced Photon Source.”