High-temperature superconductors conduct electrical currents, without any resistance, up to temperatures above the boiling point of nitrogen. One of its “champions” is Bi2Sr2Ca2Cu3O10+δ (Bi-2223), a material that is superconducting up to a critical temperature of 110 Kelvin. Though high-temperature superconductors were discovered more than two decades ago (Nobel Prize 1987), the mechanism leading to their superconducting state is still far from understood.
In a recent paper in Physical Review Letters, researchers from the University of Geneva, in collaboration with the London Centre for Nanotechnology (Bart Hoogenboom), have mapped electronic, superconducting properties of Bi-2223 at the atomic scale, using scanning tunnelling microscopy and spectroscopy. Their work focuses on the interaction between electronic properties, atomic structure and nano-scale magnetic (“spin”) fluctuations in Bi-2223.
The interaction underlying superconductivity gives rise to a forbidden region (“gap”) in the electronic spectra, but the nature of this interaction is still subject to debate. In this new work on Bi-2223, it is shown that the electronic interaction varies over the same atomic length scale as the spin fluctuations, strongly suggesting that such spin fluctuations are at the origin of high-temperature superconductivity.
This work has been published in Physical Review Letters (N. Jenkins et al, Phys. Rev. Lett. 103, 227001 (2009))
Journal link: http://prl.aps.org/abstract/PRL/v103/i22/e227001
Figure: Surface of Bi-2223 imaged at atomic resolution.