.comment-link {margin-left:.6em;}

2Physics Quote:
"About 200 femtoseconds after you started reading this line, the first step in actually seeing it took place. In the very first step of vision, the retinal chromophores in the rhodopsin proteins in your eyes were photo-excited and then driven through a conical intersection to form a trans isomer [1]. The conical intersection is the crucial part of the machinery that allows such ultrafast energy flow. Conical intersections (CIs) are the crossing points between two or more potential energy surfaces."
-- Adi Natan, Matthew R Ware, Vaibhav S. Prabhudesai, Uri Lev, Barry D. Bruner, Oded Heber, Philip H Bucksbaum
(Read Full Article: "Demonstration of Light Induced Conical Intersections in Diatomic Molecules" )

Tuesday, May 16, 2006

Superconductivity Theory Proven

Chandra Varma (Photo courtsey: UC-Riverside)

A French-German team of experimental scientists has announced that they could verify the central prediction of a high-temperature superconductivity theory proposed by a Prof Chandra Varma, currently a physics professor at the University of California-Riverside.

Superconductors are materials that conduct electricity with near-zero resistance below a specific temperature, known as the critical temperature. Superconductors typically find use in electric power transformers and magnetic resonance imaging machines. Conventional metallic superconductors must be cooled below -424 F to become superconducting.

The scientists say this verification might assist in the fabrication of materials that are superconducting at room temperature. And it will help settle a contentious, international debate on the fundamental physics of superconductivity and emergent states of matter.

Varma's initial theory, proposed in 1989 while he was working for IBM, stated the radical idea that high-temperature superconductivity and related phenomena occur in certain materials because quantum-mechanical fluctuations in those materials increase as temperature decreases. Usually such fluctuations -- determining the properties of all matter in the universe -- decrease as temperature decreases.

In 1996 Prof. Varma noted that in copper oxide materials superconductivity is associated with the formation of a new state of matter in which electric current loops form spontaneously, going from copper to oxygen atoms and back to copper. The French-Italian group directly observed the current loops in experiments involving the diffraction of polarized neutrons. In these experiments a beam of neutrons changes direction as well as the direction of its magnetization in a manner that is closely related to the geometrical arrangement of the current loops inside the material in which the beam is made to pass.

Results of this experimental verification is detailed in the May 19 issue of Physical Review Letters. Here's the abstract.

Labels: ,


Post a Comment

Links to this post:

Create a Link