But a few physicists are intent on getting as close as possible to that theoretical limit, and it was to get a better view of that most rarefied of competitions that I visited Wolfgang Ketterle's lab at the Massachusetts Institute of Technology in Cambridge.
It currently holds the record—at least according to Guinness World Records —for lowest temperature: trillionths of a degree F above absolute zero. Ketterle and his colleagues accomplished that feat in while working with a cloud—about a thousandth of an inch across—of sodium molecules trapped in place by magnets. I ask Ketterle to show me the spot where they'd set the record.
We put on goggles to protect ourselves from being blinded by infrared light from the laser beams that are used to slow down and thereby cool fast-moving atomic particles. We cross the hall from his sunny office into a dark room with an interconnected jumble of wires, small mirrors, vacuum tubes, laser sources and high-powered computer equipment. Ketterle's achievement came out of his pursuit of an entirely new form of matter called a Bose-Einstein condensate BEC.
The condensates are not standard gases, liquids or even solids. They form when a cloud of atoms—sometimes millions or more—all enter the same quantum state and behave as one. Albert Einstein and the Indian physicist Satyendra Bose predicted in that scientists could generate such matter by subjecting atoms to temperatures approaching absolute zero.
Seventy years later, Ketterle, working at M. The three promptly won a Nobel Prize. Ketterle's team is using BECs to study basic properties of matter, such as compressibility, and better understand weird low-temperature phenomena such as superfluidity.
While scientists have long suspected that there's an intrinsic 'speed limit' on the act of cooling in our Universe that prevents us from ever achieving absolute zero 0 Kelvin, It's the speed of cooling. What Masanes is referring to here are two fundamental assumptions that the third law of thermodynamics depends on for its validity.
The first is that in order to achieve absolute zero in a physical system, the system's entropy has to also hit zero. The second rule is known as the unattainability principle, which states that absolute zero is physically unreachable because no system can reach zero entropy. The first rule was proposed by German chemist Walther Nernst in , and while it earned him a Nobel Prize in Chemistry, heavyweights like Albert Einstein and Max Planck weren't convinced by his proof, and came up with their own versions of the cooling limit of the Universe.
This prompted Nernst to double down on his thinking and propose the second rule in , declaring absolute zero to be physically impossible. Together, these rules are now acknowledged as the third law of thermodynamics, and while this law appears to hold true, its foundations have always seemed a little rocky - when it comes to the laws of thermodynamics , the third one has been a bit of a black sheep.
The Cambridge lab uses this kind of refrigerator to inspect many different types of materials and material properties. Perhaps the most surprising of them is iron germanide, YFe2Ge2. At low temperatures, this iron-based material contorts into a superconductor.
Iron, he explains, typically destroys any superconducting properties in a material, regardless of temperature, due to the magnetic nature of iron. Superconductivity has many applications in science, medicine and computing, and each new superconductor can help foster novel technology.
But the group is currently in the process of developing another more efficient fridge that can sustain these low temperatures for longer. With this new fridge, the team will look at other iron based materials at low temperatures for sustained periods of time and also continue working with materials known as topological semimetals , such as ZrSiS.
The low-temperature magnetic behavior of topological semimetals is in large part a mystery, for their properties are dominated by their topology or the arrangement of its parts , not their constituent elements. And the Cambridge team is ready to unearth their enigmas once the new refrigerator is up and running. Strange physical properties thrive under the extremes of low temperature, and the implications of these bizarre qualities are seemingly boundless.
Supercooling techniques such as the ones used in dilution refrigeration are critical for a wide range of disciplines: gravitational wave research, superconductivity, spintronics, quantum computing and other up-and-coming technologies. Alleviating high temperature strains, work at absolute zero is crucial in understanding and uncovering a lot of unknowns in both quantum mechanics and physics in general.
The views expressed are those of the author s and are not necessarily those of Scientific American. Caitlin Gainey is an incoming freshman at Yale University, where she will pursue a degree in astrophysics and mathematics.
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