MadSci Network: Physics

Re: What is a 'quantum critical point' ?

Date: Sun Dec 19 15:42:56 2004
Posted By: Layne Johnson, Undergraduate
Area of science: Physics
ID: 1103313342.Ph

In physics, a critical point is the point where transitions take place. For
instance, the temperature at which ice melts into water is a critical
point, and the temperature that water boils into steam is another critical
point. The event horizon around a black hole is another example of a
critical point.

A quantum critical point is a critical point on a quantum scale. They
aren't driven by temperature (like ice to water to steam) or by gravity
(like an event horizon), but quantum fluxuations. Some metals take on
unexpected properties when quantum critical points are reached. I don't
know the specific changes that take place - this really isn't my area of
study. So let's turn to the expert.

Qimiao Si, who is mentioned in the article you read, wrote a paper in
October 2001 that explains in more detail what quantum critical points are
and how metals behave when undergoing quantum changes, and how the
experiments he and his team did could explain the latest theories in
quantum mechanics. Access to the paper is unfortunately restricted unless
one happens to be a subscriber to Nature, but a brief excerpt from it can
be read here - 

Thanks for the question,

Layne Johnson

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