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ArrowLow Temperature Physics: The What, the How, the Why

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By Kristen Coyne


What is low temperature physics? Imagine what it's like to drive through a dense fog. There are structures out there – buildings, trees, pedestrians -- but you can see these shapes only dimly, if at all.

Magnet Academy

That's what it's like for physicists who want to observe certain quantum mechanical properties – behavior that occurs at the atomic level. At normal temperatures, they can't see these behaviors. But if they make their experiments very, very cold, it's as if a mist dissipates, revealing a clearer view of what's going on.

Invisible to the naked eye, atomic particles are constantly jostling, wiggling and zipping inside all materials, getting in the way of what the scientists want to see. When you cool the particles down, however, they slow down: Liquid water molecules have less energy than molecules of water vapor, and solid ice holds less energy than water. When a material is cold enough, scientists can see some really neat stuff: heavy fermions, the quantum hall effect and exotic phase transitions.

Scientists in the Millikelvin Facility
MagLab staffer Eun Sang Choi (left) assists West Virginia University scientist James Rall with an experiment in the Millikelvin Facility.

It takes a lot more than a Frigidaire to sedate atoms sufficiently for this kind of study. The fields of low-temperature and ultra low-temperature physics deal in degrees far below anything found in the natural universe – way down to almost -273 degrees Celsius (-460 degrees Fahrenheit). Scientists, though, prefer a different temperature scale called Kelvin. This scale literally starts from zero: 0 K (absolute zero) is as cold as cold can be, a condition that has not even been achieved in a laboratory.

We have, however, come pretty close. As a matter of fact, two facilities at the National High Magnetic Field Laboratory are dedicated to creating extremely low temperatures on a daily basis, so that scientists can see what happens when a material is cooled to the point of almost no thermal motion, then put inside a strong magnetic field. The particles in the material respond to the magnetic field in a way that can reveal fascinating secrets about matter.

At the MagLab's Millikelvin Facility in Tallahassee, scientists conduct sensitive experiments at temperatures within 7 thousandths of a Kelvin above absolute zero. If that number doesn't give you a brain freeze, try this: In the MagLab's High B/T Facility, located at the University of Florida's Microkelvin Laboratory in Gainesville, experiments can be conducted within 40 millionths of a Kelvin above absolute zero.


Powers of Ten

Decimal

Exponential

Prefix

0.1 (tenth) 10-1 deci
0.01 (hundredth) 10-2 centi
0.00.1 (thousandth) 10-3 milli
0.000001 (millionth) 10-6 micro
0.00000000.1 (billionth) 10-9 nano
0.000000000001 (trillionth) 10-12 pico


How do you create such a frigid environment?

Next Page ArrowThe How: Zeroing in on Zero

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