A theoretical physicist is seeking a way of applying quantum theory to the world in which we live, writes Dick Ahlstrom
Things can get very complicated when you dig down into matter to the level of atoms. It is a place where antimagnets can have magnetism and where electrons can have an inherent "handedness".
Dr Ben Braun studies this strange nano world and recently made important new discoveries about the spin direction of electrons around ferromagnetic atoms and how they can be "chiral" or left- and right-handed.
This research area is a crossing point for quantum and classical physics, says Dr Braun. "Magnetism is a quantum mechanical effect, but magnetism is usually treated as classical [ mechanics]," he explains. "Now we are trying to go back and see where the quantum signature works. I am coming from the classical side and trying to find the quantum signature."
Braun is codirector of theoretical physics within the school of physics at University College Dublin. His work is funded by Science Foundation Ireland and he holds an SFI principal investigator award.
Although his research is exotic, market potential is always close given interest in the use of "spin electronics" and other quantum related effects within the computer industry. "In general my work is in nanoscale magnetism and spintronics," he says. "All of these effects we try to exploit commercially."
While he mostly does theoretical work, he and colleagues travelled to Grenoble in France to use the world's most powerful neutron source to study a disordered quantum magnet. The goal was to see if the theoretical chiral nature of electron spin states could be proven with experimental results, something that hadn't been done before.
Condensed matter physicists had long conjectured that this chirality of electron spin states would be found.
Using neutron scattering experiments, Dr Braun confirmed through direct experimental evidence how chirality emerges in a disordered quantum magnet. It showed that chirality is an emergent property of quantum matter. The team published their findings in a recent edition of the journal Nature Physics.
In effect they revealed a "hidden" order present within the magnetic material. Magnets are inherently ordered, with electrons marshalled so that their magnetic moment matches up, thus making the material magnetic.
Non-magnetic materials do not have this order, but Braun's work revealed that an order can be present at the nano scale even if the material involved has no apparent magnetism.
He found that the electron spins in his model material were organised antiparallel to each other, giving rise to antiferromagnetic ordering. One magnetic moment cancelled out the next, and so on. Dr Braun also found that they were chiral, like matching left and right gloves that provide a mirror image of one another without being the same. "My research showed that such spin currents are inherent in antiferromagnetism," Braun explains.
The results were general enough to allow him to argue that this form of chirality could occur in many systems, providing the first example of a new state of matter.
It also has important implications for a wide range of applications, from the next generation of advanced "quantum" computers to the production of new high temperature superconducting materials.