TrendSuperconductivity at room temperature a step closer

Published 7 June 2007

Transporting energy without any loss: Scientists have been dreaming about the possibility — and its benefits — for decades, and CNRS rsearchers have made an important breakthrough toward making this dream a reality

Next to mastering cold fusion, one of the more challenging — and beneficial — goals scientists have been trying to achieve is transporting energy without any loss. If we could develop superconducting materials which worked at room temperature, we would be able to benefit from traveling in magnetically levitated trains and carrying out medical imaging (MRI) with small-scale equipment, among other things.

Well, we are a step closer to this superconductivity. Researchers at the Paris-based Centre National de la Recherche Scientifique (CNRS) have revealed the metallic nature of a class of so-called critical high-temperature superconducting materials. The result was published in the 31 May 2007 issue of Nature (see reference below), and it is no exaggaration to say that scientists have been eagerly waiting for it for more than twenty years. (Coming back to the benefits of superconductivity, CNRS, in announcing the beakthrough and its potential benefits, used the term “realizing a dream”: “un rêve qui se concrétisera lorsque l’on disposera de matériaux supraconducteurs à température ambiante”).

Superconductivity is a state characterized by zero electrical resistance and impermeability to a magnetic field. It is already used in MRI devices, and could find many applications in the transport and storage of electrical energy without loss, the development of transport systems based on magnetic levitation, wireless communication, and even quantum computers. Such applications are currently limited by the fact that superconductivity only occurs at very low temperatures. Indeed, superconducticity was discovred in 1911 the process of trying to liquefy helium, which requires a temperature of 4.2 kelvins (-269 °C) (the Dutch physicist Heike Kamerlingh Onnesa won the 1913 Nobel Prize for the discovery).

More than seven decades later, in 1987, German physicist J. Georg Bednorz and Swiss physicist K. Alexander Müller jointly won the Noble Prize for their important break-through in the discovery of superconductivity in ceramic materials. During the past twenty years or so, researchers have obtained high temperature superconducting materials, with some of these compounds becoming superconducting simply by using liquid nitrogen (77 K, or -196 °C). To date, the record critical temperature (the phase transition temperature below which superconductivity occurs) is 138 K (-135 °C). The slow progression toward ever-higher superconductivity temperature has encouraged scientists to believe that it would not be beyond of the realm of the possible to obtain materials which are superconducting at room temperature.

CNRS reports that researchers at the Toulouse, France-based Laboratoire National des Champs Magnétiques Pulsés (LNCMP), working with researchers at Sherbrooke, were able to build on their experience in working with intense magnetic fields to “quantum oscillations.” The subjected their samples to a magnetic field as intense as 62 teslas (a million times stronger than the Earth’s magnetic field), at very low temperatures (between 1.5 K and 4.2 K). The magnetic field destroys the superconducting state, and the sample, now in a normal state, showe an oscillation of its electrical resistance as a function of the magnetic field. Such an oscillation is characteristic of metals, and it means that, in the samples that were studied, the electrons behaved in the same way as in ordinary metals.

The discovery will allow for a more effective sorting out of the many theories which had been offered to explain the phenomenon, and also offer a way toward a more robust foundation on which to fashion a new theory. As importantly, it will make allow scientists to begin to think about designing more efficient materials, with critical temperatures now closer to room temperature.

-read more in Nicolas Doiron-Leyraud, Cyril Proust, David LeBoeuf, Julien Levallois, Jean-Baptiste Bonnemaison, Ruixing Liang, D. A. Bonn, W. N. Hardy, and Louis Taillefe, “Quantum Oscillations and the Fermi Surface in an Underdoped High-Tc Superconductor,” Nature 447 (31 May 2007): 565-68 (su. req.)