Friday, February 27, 2009

Hidden Order Problem Solved

I was not sure that this was worth posting on until I had read it a couple of more times and digested what I was reading. Not only is the problem of theoretical explanation solved but an applications door is opening that suggests that a major advance on mastery of superconductivity is close on the horizon.

It is anyone’s guess regarding where this will take us but understanding the underlying physics is a great start. I suspect that we will be able to design superconducting behavior into a thin layer of atoms. Maybe even print it some day.

We have had a cascade of pertinent developments in nano construction methods these past few months and the understanding of behavior at that scale. There is plenty to be done, but we can be certain that this is the real future of research in physics for decades to come.

“One of the most important problems in materials science solved”

[Published 2009-02-23]

Together with three colleagues Professor Peter Oppeneer of Uppsala Univeristy has now explained the hitherto unsolved mystery in materials science known as ‘the hidden order' - how a new phase arises and why. This discovery can be of great importance to our understanding of how new material properties occur, how they can be controlled and exploited in the future. The findings are published in the scientific journal Nature Materials.

For a long time researchers have attempted to develop the superconducting materials of the future that will be able to conduct energy without energy losses, something of great importance to future energy supply. But one piece of the puzzle has been missing. There are several materials that evince a clear phase transition in all thermodynamic properties when the temperature falls below a certain transitional temperature, but no one has been able to explain the new collective order in the material. Until now, this has been called the hidden order.

"The hidden order was discovered 24 years ago, and for all these years scientists have tried to find an explanation, but so far no one has succeeded. This has made the question one of the hottest quests in materials science. And now that we can explain how the hidden order in materials occurs, in a manner that has never been seen before, we have solved one of the most important problems of our day in this scientific field," says Professor Peter Oppeneer.

Four physicists from Uppsala University, led by Peter Oppeneer and in collaboration with John Mydosh from the University of Cologne, who discovered the hidden order 24 years ago, show through large-scale calculations how the hidden order occurs. Extremely small magnetic fluctuations prompt changes in the macroscopic properties of the material, so an entirely new phase arises, with different properties.

"Never before have we seen the so-called ‘magnetic spin excitations' produce a phase transition and the formation of a new phase. In ordinary material such excitation cannot change the phase and properties of the material because it is too weak. But now we have shown that this is in fact possible," says Peter Oppeneer.

What explains in detail all of the physical phenomena in the hidden order is a computer-based theory. Among other applications, it can be used to better understand high-temperature superconducting materials and will thus be important in the development of new superconducting materials and future energy supply.

For more information, please contact:

Peter Oppeneer, professor at the Department of Physics and Materials Science, phone: +46 (0)18-471 37 48; cell phone: +46 (0)709-60 40 16; or

Article abstract

Nature Materials

Published online: 22 February 2009
Corrected online: 26 February 2009 doi:10.1038/nmat2395

Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking

S. Elgazzar
1,3, J. Rusz1, M. Amft1, P. M. Oppeneer1 & J. A. Mydosh2


Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu2Si2, where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.

Department of Physics and Materials Science, Uppsala University, Box 530, S-751 21 Uppsala, Sweden
II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
On leave from: Faculty of Science, Menoufia University, Shebin El-kom, 32511, Egypt
Correspondence to: P. M. Oppeneer
1 e-mail:
* In the version of this article initially published online, the caption for Figure 2 was incorrect; it has now been corrected on all versions of the article.

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