21 April 2014

The quest for absolute zero in a magnetic field

MagLab scientist Tim Murphy will talk about extremely cold temperatures and why physicists into quantum mechanics really dig them.


TALLAHASSEE, Fla. — Tallahassee sizzles in the summer — but even on its hottest days, there are places in the MagLab where things are totally chill. That’s especially true in physicist Tim Murphy’s lab, where there’s a special refrigerator iced down to a frosty negative 459 degrees Fahrenheit. (Yes, you read that temperature correctly.) And Murphy, a 20-year MagLab veteran, wouldn’t have it any other way.

Tim MurphyPhysicist Tim Murphy adjusts one of the three magnets in the MagLab’s Millikelvin Facility, where scientists routinely observe the behavior of materials at the atomic level.If you’re curious as to why Murphy is so keen on cold temperatures — and why he has a fridge that keeps stuff so crazy cold — head to the MagLab’s next Science Café on Tuesday, May 6, from 6:15 to 7:30 p.m. at the Backwoods Bistro. It’s the lab’s last café of the 2013-2014 school year, so arrive early if you want to grab a good seat and something tasty to eat before the show begins.

Murphy, like many physicists, is interested in how the world works on the quantum (or teeny, nano-sized) level. That’s also why he’s interested in extreme temperatures. At super cold temperatures, the atoms inside matter slow down enough for scientists to observe what’s going on at the “ground state,” or the very lowest-energy state of matter.

“That is the key: the ground state of a material,” said Murphy, who is the MagLab’s director of the Direct Current Field Facility. “The ground state of a material tells you its underlying physics.”

At the warm, comfy temperatures where we humans live and interact with matter, Murphy said, “everything is all clouded up … everything is moving very fast. That washes out all the quantum mechanical effects in the materials we're studying.”

Try this: Think of thermal energy as a blanket of fog.

“Imagine that you’re driving down the road on a really foggy morning,” Murphy said. “You know that there are buildings and trees and structures all around you, but you just can’t see them because of the fog. That fog is the equivalent of the thermal motion. If you take that fog away — reduce the temperature — then you can see the structure that is there, has always been there, but was washed out by the fog. When you reduce the temperature, you can see the underpinnings of what was always there but was being washed out by the thermal fog.”

Murphy uses that special refrigerator in his lab — the one that gets very close to “absolute zero,” or negative 459.7 degrees F — to probe the ground state of any material he puts inside it. He also introduces a high magnetic field to the mix, and then the party really gets started.

Want to learn what kind of strange stuff happens then? Bring all your very coolest questions to the last science café of the season. See you there!

The National High Magnetic Field Laboratory is the world’s largest and highest-powered magnet facility. Located at Florida State University, the University of Florida and Los Alamos National Laboratory, the interdisciplinary National MagLab hosts scientists from around the world to perform basic research in high magnetic fields, advancing our understanding of materials, energy and life. The lab is funded by the National Science Foundation (DMR-1157490) and the state of Florida. For more information, visit us online at nationalmaglab.org or follow us on Facebook, Twitter, Instagram and Pinterest at NationalMagLab.