|SUPERSTRIPES NEWS Vol. 1, No. 1 January, 2001
The stripe critical point
Last news on the struggle to explain high temperature superconductivity: the solution of the PHASE DIAGRAM OF THE NORMAL PHASE. A key step toward the solution of the puzzle that keep the scientists busy since 1986 has been made on Dec18, 2000 by an international team (Italian, Japanese and American) in a collaboration supported by Italian agencies CNR, INFM and MURST. The experiment provides an answer to the hot topic debated this year: "stripes YES or NOT".Antonio Bianconi and his co-workers in the article that appeared on the English Journal Physics: Condensed Matter Vol.12, page 10655-10676, fired synchrotron radiation x-rays to probe quantum atomic fluctuations of the stripes, rivers of charges in a inhomogeneous two dimensional metal, in the time scale of picoseconds. They have found a hidden variable: the "micro-strain" of the Cu-O bond due to the mismatch between the copper oxide and the rare earth oxide sub-lattices. This new physical variable drives the critical temperature for stripe formation to zero reaching a quantum critical point (QCP). This is the origin and source of the quantum fluctuations observed by several groups in superconducting samples in these last ten years.
The highest critical temperature in all cuprate perovskites, Tc=135 K is reached at the quantum critical point for the formation of fluctuating (on a time scale of picoseconds) bubbles (of diameter 100-300 Ä) of quantum stripes (about 1.5 nanometer width). In these metallic stripes at "shape resonance" the hopping between stripes is easier for electron pairs than for single electrons (Superstripes and superconductivity, YES). At higher values of the micro-strain where insulating ordered crystals of polaron strings are formed the superconductivity is quenched (Stripes and No superconductivity).
Graham P. Collins in Scientific American August 200 pag.22
Michael Brooks in New Scientist, 26 June1999, No.2192
The related paper of the Roma Group presented at the Stripes2000
Conference can be downloaded in the PDF version by clicking The stripe critical point
The book of Abstracts of the third international conference "Stripes
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