Pegor Aynajian, whose research focuses on quantum phase transitions, will receive $531,582 over five years through the NSF’s CAREER program, which supports early-career scientists.

Aynajian starts with a simple magnet you might find on your refrigerator when he explains phase transitions. “If you raise the temperature above its critical temperature, it becomes a regular metal,” he says of the magnet. “It won’t stick anymore. That’s called a phase transition.”

Specifically, that’s a thermal phase transition, just like the transition from water to ice. That’s a transition we see all the time. Now consider what would happen if we took a fridge magnet and cooled it to absolute zero, zero Kelvin (or −459.67 degrees Fahrenheit). Achieving a phase transition at absolute zero, say by tuning some parameter, can be remarkable, Aynajian says. Rather than thermal, though, it’s called a quantum phase transition.

“Near quantum phase transitions, new states of quantum matter are born,” he says. “We call it the physics of emergence.”

Under those conditions, scientists have found novel electronic phases — including superconductors — that aren’t seen otherwise.

Superconductors are materials that conduct electricity with absolutely no resistance, when cooled below a certain temperature.

This funding will accelerate Aynajian’s research into discovering emergent phases of matter with an emphasis on “unconventional” superconductors. He’s also interested in ferromagnetic superconductors, which are rare and poorly understood.

Aynajian’s group built a scanning tunneling microscope (STM), which uses quantum physics to “see” electrons on the surface of a sample. With this tool, they can observe the spatial patterns electrons form near a quantum phase transition. Many materials have never been studied this way before.

Aynajian’s group also uses X-rays and neutrons at research facilities around the world.

“Our STM is giving us new and unprecedented experimental results,” Aynajian says. “We can see what electrons do, how they form a new state of order, which did not exist before. Our next goal is to figure how we can ‘twist’ this order to create a new superconductor. Working directly with theorists helps us find ways to understand them further.”

Superconductors, which physicists have been studying for about a century, work at very low temperatures, which is a challenge to their practical use. In the past 30 years or so, physicists have found some materials that are superconductors at somewhat higher temperatures. If scientists can find a “room-temperature” superconductor, it would be a tremendous breakthrough for the electric grid and electronic devices of all kinds. That sort of technology could save billions of dollars in energy costs, Aynajian says.

Aynajian, who joined Binghamton’s faculty in 2013, began studying superconductors in graduate school and continued working with them during a post-doctoral fellowship at Princeton University. He credits Bernhard Keimer, his graduate school mentor at Germany’s Max Planck Institute for Solid State Research, with bringing him into the field.

The CAREER award will give Aynajian an opportunity to do some mentoring of his own, both with his graduate students and with children in Greater Binghamton. He plans to develop hands-on experiments and playful activities with superconductors, including a mini magnetic-levitation train, to inspire area students and offer some exposure to ideas in physics.

As for the experimental aspect of the project, he’s optimistic. “No matter what we find,” he says, “it will be interesting.”

Michael Lawler, a theoretical physicist at Binghamton University, contributed to the research, which he considers a great achievement for the experimentalists on the team.

The researchers use a very small tool, bringing its tip close to a sample of material they want to examine. They then apply a voltage between them and try to drive a current. In this experiment, Lawler explained, they were able to change the tip by picking up a nano-sized “flake” of a material with a normal metallic tip so they could apply voltage from one superconductor to another.

Superconductors are materials — either “conventional” or “bad” metals at ambient temperatures — that conduct electricity without resistance below a certain temperature. For decades, it was thought that these materials could conduct electricity only at temperatures far below freezing. Since the mid-1980s, however, scientists have discovered several compounds that superconduct at much higher temperatures.

Lawler and his colleagues study a class of materials called cuprate superconductors, compounds including copper and oxygen that superconduct at relatively high temperatures (below 90-150 Kelvin). This particular experiment operated at about 50 millikelvin, which is about as cold as the research group can go, to reduce noise in the measured current.

“This is a better and different way of looking at these cuprate materials than has previously been possible,” says Lawler, who compared the new technique to the difference between looking at stars with a telescope and looking at the X-rays stars produce.

Scanning tunneling microscopes (STM) with a superconducting tip allowed the group to observe the surface of these materials in a completely new way.

“Before now, what we’ve known is that there are lots of waves present in these materials. You can think of the charge changing in a wavelike pattern, where the wave is 4 atoms across.”

In this experiment, the team was able to look at the superconductivity at the atomic scale for the first time. “They’re observing that superconductivity can have waves in itself,” Lawler says. “And that’s the first time that’s ever been observed.”

If you look at the amplitude of the wave, it’s relatively modest. “It didn’t surprise me, though people were hoping for something more dramatic,” Lawler says.

These experiments suggest that other materials — “tuned” with different amounts of oxygen — could produce different results, possibly more dramatic waves.

In principle, a room-temperature superconductor could allow electricity to travel with zero energy loss from power plants to houses and make possible advanced high-speed trains and cell phone towers. Physicists are still working to understand the origin of high-temperature superconductivity.

“I’m excited about seeing this wave that we can now probe directly,” Lawler says. “We can find out if there are materials where this dramatic wave happens. They would be different kinds of superconductors than we typically study.”

In addition to Binghamton University, the team included scientists from Harvard University, Cornell University, University of St. Andrews, Seoul National University, the Institute of Basic Science in Seoul, the Institute of Advanced Industrial Science and Technology in Japan, the University of Tokyo, the Max Planck Institute for Chemical Physics of Solids and Brookhaven National Laboratory.

In 2009, while he was a post-doctoral fellow at Princeton University, Aynajian used a scanning tunneling microscope (STM) to observe the movement of electrons on the surface of a high-temperature superconductor. “The electrons order themselves in beautiful charge patterns before transforming into a high-temperature superconductor,” he says.

Using intense X-rays, Aynajian and his collaborators observed these patterns within the bulk of the superconductor. This breakthrough led to the 2014 publication of a paper titled “Ubiquitous Interplay between Charge Ordering and High-Temperature Superconductivity in Cuprates” in Science.

“Pegor spent years honing the technology to catch electrons in the act of forming these so-called ‘crystals’ that move in unison,” says Ali Yazdani, a Princeton professor who supervised Aynajian’s work there. “We don’t yet have a clear understanding why these materials superconduct, but we think it comes from the strong interactions between electrons. That’s what Pegor is trying to sort out, and why this work is so important. He’s able to synthesize many different ideas, and … he’s already made a big impact in the field.”

Aynajian received his bachelor’s degree from Lebanese University in Beirut and his doctorate from the University of Stuttgart in conjunction with the Max Planck Institute for Solid State Research in Germany.

Since arriving at Binghamton in 2013, Aynajian has been setting up a below-ground, ultra-quiet lab, with undergraduate and graduate students constructing Binghamton’s own scanning tunneling microscope. Two semesters later, their STM has passed its first tests of visualizing carbon atoms on graphite and electron waves on copper. This gives sophomores their first view of the quantum world.

“It’s like exploring a new world, like landing on the moon for the first time,” says Aynajian, an assistant professor of physics. “But instead of the cosmos, you’re going to the microcosmos, to the quantum world. You land on a new sample, and for the first time you’re able to see what electrons actually do on this particular material, which makes it so special. That’s a tremendous excitement, but the real reward doesn’t come until you can explain what’s happening.”

A Binghamton University physicist and his colleagues say they have unlocked one key mystery surrounding high-temperature superconductivity. Their research, published this week in the

Michael Lawler, assistant professor of physics at Binghamton, is part of an international team of physicists with an ongoing interest in the mysterious pseudogap phase, the phase situated between insulating and superconducting phases in the cuprate phase diagram.

“Evidence has been accumulating that this phase supports an exotic density wave state that may be key to its existence,” the physicists write in the new journal article. A density wave forms in a metal if the fluid electrons themselves crystalize.

Using a scanning tunneling microscope (STM) to visualize the electronic structure of the oxygen sites within a superconductor, the team found a density wave with a d-orbital structure. (The electron density near each copper atom looks a bit like a daisy in the crystallized pattern.) That’s especially surprising because most density waves have an s-orbital structure; their electron density is isotropic. “It’s not the pattern you would expect,” Lawler says.

In this research, Lawler and his colleagues focused on a member of the cuprate class of superconductors called bismuth strontium calcium copper oxide (BSCCO). “We now believe these density waves exist in all cuprates,” says Lawler, a theorist whose contribution to the research involved subtle uses of the Fourier transform, a mathematical analysis that’s useful when examining amplitude patterns in waves.

Superconductors conduct electricity without resistance below a certain temperature. For decades, it was thought that these materials could conduct electricity only at temperatures far below freezing. Since 1987, however, scientists have discovered several compounds that superconduct at much higher temperatures.

Development of this technology could lead to near lossless delivery of electricity to homes and businesses as well as to improvements in cell phone tower receptions and even high-speed trains. 

Aleksey Kolmogorov, assistant professor of physics at Binghamton, proposed the new superconductor in Physical Review Letters in 2010 and then teamed up with leading experimental groups in Germany, Belgium, Italy and France to test the prediction.

The synthesized material — a novel iron tetraboride compound — is made out of two common elements, has a brand-new crystal structure and exhibits an unexpected type of superconductivity for a material that contains iron, just as predicted in the original computational study.

“Paradigm-shifting superconducting materials have so far been discovered experimentally, and oftentimes accidentally,” Kolmogorov says.

Until now, theory has been used primarily to investigate superconducting mechanisms and, in rare cases, suggest ways that existing materials might be modified to become superconductors. But many proposed superconducting materials are not stable enough to form and those that do form are poor superconductors.

Superconductors, which conduct electric current without any resistance when cooled below a certain temperature, have many interesting applications. For instance, power lines made out of superconducting materials can significantly reduce the energy lost in transmission. Superconducting magnets are also used in high-speed levitating trains and could improve wind turbines.

The phenomenon of superconductivity was discovered more than 100 years ago, with breakthroughs in the 1960s bringing it into practical application in a variety of technologies. The critical temperature, or Tc, for superconductors discovered to date is between 0 and 136 Kelvin (-460 and -214 degrees Fahrenheit). This means that most superconductors require expensive cooling mechanisms. Scientists are still searching for new materials that are superconductors at higher temperatures and can be mass produced.

More than five years ago, Kolmogorov, then at Oxford University, began studying boron-based materials, which have remarkably complex structures and a wide range of applications. He developed an automated computational tool to identify previously unknown stable crystal structures without any input from experiment. His “evolutionary” algorithm emulates nature, meaning it favors more stable materials among thousands of possibilities. (Kolmogorov is a computational physicist, but he also dreams of holding a compound in his hands that he predicted in silico.)

The search revealed two promising compounds in a common iron-boron system, which came as a surprise. Moreover, graduate student Sheena Shah’s calculations indicated that one of them should be a superconductor at an unusually high temperature of 15-20 Kelvin for the considered (so-called “conventional”) type of superconductivity.

Months of double-checking confirmed the preliminary results on the stability and superconductivity of the compound. Still, the 2010 theoretical discovery was met with skepticism.

Natalia Dubrovinskaia and Leonid Dubrovinsky, professors at the University of Bayreuth in Germany, undertook a year-long series of challenging high-pressure experiments and produced a very small quantity of iron tetraboride in the predicted crystal structure, leading to the most recent journal article. Detailed measurements also demonstrated the material’s predicted superconducting property and, unexpectedly, its exceptional hardness.

“The discovery of this superhard superconductor demonstrates that new compounds can be brought into existence by revisiting seemingly well-studied systems,” Kolmogorov says. Now that this material has been synthesized, it may be possible to modify it and raise the temperature at which it becomes a superconductor.

Next, Kolmogorov plans to turn his attention to metal oxides. “They are fascinating because they have applications as catalysts, photovoltaic materials and protective coatings,” he says. “We hope our predictive methodology will lead to more exciting discoveries.”