The Materials Guy
Jak Chakhalian became a physicist because, he says, he wants to understand the very internal workings of the universe.
“As a scientist, my goal is to always push things to the extreme,” he said. He likens doing science to climbing the most challenging mountains. “You have to be very fit so that you can reach the highest heights, and then you see things that other people don’t see.”
Chakhalian already has seen things others have never seen. In 2007, he created an artificial material using a ferromagnet and a high-temperature superconductor, two of the most complex materials among modern functional materials. He found that when he combined these two poorly understood materials into something that does not occur in nature, he could learn some things about the two materials otherwise not possible to understand by studying them individually. Science magazine cited his findings as one of the top 10 scientific breakthroughs of the year.
However, the mountain remains to be scaled. Chakhalian seeks the “peak challenge” in condensed matter physics: room-temperature superconductivity. To explain the challenges of understanding the possibility of room-temperature superconductivity, he points to rust as an example.
Rust, or iron oxide, has a lot in common with most of the interesting materials pursued by today’s scientists. In rust, if one electron does something, all of the other electrons “know” it. This phenomenon, called correlated electrons, to a much lesser degree exists in semiconductors, magnets, and other materials that run computers, televisions and complex medical equipment, drive cell phones and keep the electricity on in your home.
“In normal materials used today, electrons don’t care about the movement of one another,” Chakhalian said. “We can predict their properties practically on the ‘back of an envelope’ with the help of powerful computers.” However, with correlated materials, the calculations for the movement of one electron involve tracking the interactions with billions of electrons.
“Imagine that by telling you something, the other six billion people would react to it collectively,” Chakhalian said. “You just can’t calculate this.”
To understand correlated materials, scientists face two challenges: First to understand these materials experimentally and second to describe them with the ultimate goal to control their properties. To do that, Chakhalian creates artificial materials at the atomic scale to shed light on the properties of these extremely correlated materials. At the nanoscale, the proportion of surface to bulk dramatically decreases, and scientists can study interactions that occur at the interface between these materials, which may result in new quantum phenomena.
So in 2007, Chakhalian put together a superconductor and a ferromagnet, a combination of materials never found in nature now known as a never-seen-before superconducting ferromagnet.
“Surprisingly, we found that you could use two very complex materials and make something that is easier to understand,” he said. He and a colleague at Argonne National Laboratory also invented a novel way to look at single atomic orbitals at the interface between the two materials.
“On the top of very complex experiments, the theoretical challenge is how can you describe the ‘gazillions’ of electrons in an artificial crystal that are strongly correlated,” Chakhalian said. “If you did, basically there would be no limit to what we could do with these materials.”
Take a Prius, for instance, which runs in part on thermoelectric power of correlated oxide of cobalt. Chakhalian and his team have created an artificial material that increases the efficiency of thermoelectric power five-fold. New thermoelectric superstructures also could potentially be used to cool CPUs in computers. Modern computers have multiple core processors because faster speeds mean hotter temperatures and eventually at great speeds processors would melt. However, the thermoelectric layers of nanomaterial will ‘self-cool’, and if placed nearby a computer’s central processing unit could allow for ever faster computer processing. That means that once again, computers could become smaller, faster and smarter than they are today.
Chakhalian’s lab also investigates phase change materials, which are materials that become something different under external stimuli. For example, you can create a phase change material called a non-Newtonian liquid at home by combining equal parts of cornstarch and water in a pie tin. The substance looks gooey and sloshes around like a liquid. However, if you apply pressure by banging the liquid with a hammer, it shatters like glass.
“Under pressure all of a sudden the liquid becomes solid,” Chakhalian said. Right after the pressure lifted, it begins to pool again.
No less dramatic phase changes also take place in materials with correlated electrons. Chakhalian has found that by shining a laser beam on such materials, scientists can make conducting metals change into insulators in a few femtoseconds — 10,000 times faster than the current reaction time of any used in today’s computer materials. This could radically change the response time of microelectronic devices and speed up calculations that could solve today’s complex scientific problems.
“It is incredible to realize that light, or an electric field, can freeze or unfreeze the electrons, which allow us to turn the very same material from a conductor to insulator.” Chakhalian said.
But Chakhalian downplays these findings. His focus remains on what he sees as the ultimate summit in condensed matter physics: room temperature superconductivity.
“I’m after the big thing,” he said. “With room temperature superconductivity you can levitate trains, cars, cranes – anything, really – with no friction and no motor, no oil or gas.”
Room temperature superconductivity would change the world’s economy, Chakhalian contends. To start, superconductors can carry electricity without losing energy to heat, which the current materials used at room temperature cannot do. Today’s power grid loses almost 15 percent of its energy to heat. That may not seem like a high number, but it translates into a multi-billion dollar loss. Scientists have looked at many solutions to increase energy efficiency, but Chakhalian seeks radical energy solutions, like a material that acts as a room temperature superconductor.
“With a superconductor, you could redistribute energy around the globe with zero loss,” he said.
In Japan, high-temperature superconductors drive experimental trains called Maglev at speeds close to the speed of airplanes. However, the logistics of cooling these superconductors to lower temperatures using liquid nitrogen make using them on a large scale logistically impossible.
Chakhalian currently has $1.2 million from the Army Research Laboratory to aid him in his quest. To get there, he will continue to look at the interfaces and surfaces of artificial complex oxide materials that he creates at the nanoscale.
“The interface is the new playground. It is a powerful control tool,” he said.
Like the first humans to ascend a mountaintop, Chakhalian doesn’t know yet what he will find.
“It’s a scientific endeavor. It’s not a factory,” he said. “What’s at the end of the production line? I don’t know.”
But if it is room temperature superconductivity, Chakhalian knows one thing: “If we ever achieve this, the world will change very rapidly.”
Chakhalian knows that he may not find what he is looking for. However, he feels he owes it to society to seek the radical solution to today’s problems.
“You’re risking everything” trying to address problems that may have no solution. “But as a scientist, my goal is to always push to the extreme of unknown.”