High-temperature superconductivity

Superconductivity is a physical property whereby a material offers zero electrical resistance when cooled below a certain temperature. Discovered in the early 20th century, the potentially life-changing principle offers the prospect of vastly improving the storage of memory devices, greatly accelerating transportation, and radically reducing the financial and environmental costs of energy transmission.

It would be difficult to exaggerate IBM’s pioneering role in the area. The company has funded primary research into superconductivity for many decades. A duo of IBM researchers, Alex Müller and Georg Bednorz, earned the Nobel Prize in Physics in 1987 for their exploratory superconductivity work, which spawned a frenzy of inquiry that continues to this day.

IBM scientists have advanced the field and opened the door to multiple commercial applications — from magnetic resonance imaging (MRI) and high-speed rail to lighter, smaller wind turbines and more-efficient smart energy grids — while stimulating the collective imagination about untold applications to come. “A superconductor wire the size of your thumb,” explained IBM Research scientist Kevin Roche, “could carry as much power, more efficiently, than a copper cable the thickness of your arm.”

A wasteful heat surrounds us. The heat of your laptop, for example, is a by-product of the device’s inefficient use of energy. As electricity passes across a computer’s circuits and through its wires, it meets resistance. This friction creates heat. While it may only be inconvenient to a laptop user, this phenomenon proves incredibly costly at scale. The electric power industry loses more than 5% of energy during transmission, squandering billions of dollars and vast amounts of resources along the way.

Here is where superconductivity offers a potential solution. Imagine the difference between sliding a hockey puck across a bumpy old linoleum floor versus across a sheet of ice. As a conveyance mechanism, or conductor, the linoleum saps energy from the puck and impedes its travel. By contrast, the ice is far more efficient, enabling the puck to travel faster and farther.

Now, instead of a puck, think of a series of electrons flowing in an electrical current. When Müller and Bednorz began their research, the world only had the equivalent of linoleum floors — copper or aluminum wire, for instance. They were slippery, but not frictionless, causing a drop in voltage from one end of a wire to the other. So the duo set out in search of a material that would offer zero resistance under proper conditions, enabling electricity to flow without dissipating power or exhausting heat.

They were hardly the first scientists to explore superconductivity. In 1911, Dutch scientist Heike Kamerlingh Onnes discovered that at low temperatures, electrons could induce vibrations that would draw them together, creating couples known as Cooper pairs, which swarm in ways that allow them to pass through metals without resistance. As temperatures rise, however, particle movements interfere with the electron flow. Onnes revealed that zero electrical resistance could be achieved when using certain alloys and chemical compounds that were cooled close to absolute zero — in his case, 4.19 Kelvin for liquid mercury. (Absolute zero is 0 Kelvin (K), -273 degrees Celsius (C), or -459 degrees Fahrenheit (F).) In subsequent decades, superconductivity was found in lead at 7 K, in niobium at 10 K, and in niobium nitride at 16 K.

Scientists doggedly scouted for materials that would confer superconductivity at more practical temperatures. But progress was slow. New discoveries typically improved temperature thresholds by only fractions of degrees. In the early 1970s, progress stalled out at 23 Kelvin. John Armstrong, IBM vice president and director of Research, said the field was “believed to be mature, understood and dormant.”

But in the 1980s, Bednorz, a former IBM intern, returned to the company to work with his mentor, IBM Fellow Müller, and things began to change. They noticed that perovskites, a class of oxides, offered promise. They added barium to crystals of lanthanum-copper-oxide to produce a chemically stable ceramic that demonstrated superconductivity at 35 K. Deemed the first successful high-temperature superconductor, or HTS, it represented an important achievement because 35 K required far less cooling with liquid helium (4.2 K), a very limited resource. It also represented a leap toward 77 K, the point at which superconductors can be cooled with liquid nitrogen, which can be condensed from air using common refrigeration techniques.

In January 1986, Müller and Bednorz revealed their discovery to the scientific community, unleashing a flurry of activity among physicists who imagined exciting new applications in electrotechnology and microelectronics. Within a year, several groups had prepared their own versions of the IBM compound and reported similar results. By March 1987, thousands of scientists and engineers were researching other versions of the new class of oxide superconductors. “This discovery is quite recent, less than two years old,” said Gösta Ekspong of the Royal Swedish Academy of Sciences in late 1987, “but it has already stimulated research and development throughout the world to an unprecedented extent.”

Müller and Bednorz were honored that year with the Nobel Prize. It was the shortest elapsed time ever between a discovery and the award for any scientific Nobel. That same year, the company named Bednorz an IBM Fellow.

The quest to fully harness the potential of high-temperature superconductors continues today, with a focus primarily on power transmission, high-speed rail and other novel modes of frictionless transportation such as magnetic levitation trains. Many countries are testing energy-efficient power cables using HTS. Nearly every hospital now employs MRIs using small superconducting coils to produce a rotating magnetic field that creates detailed images of the human body. Some countries are even testing trains that use onboard magnets to levitate vehicles above steel rails, potentially making trains much faster and more efficient.

The key to fully unlocking the potential of superconductivity and deploying it widely will be discovering materials that express superconductivity at more typical ambient temperatures. A group of physicists recently achieved a theoretical breakthrough by using a novel metallic compound of hydrogen, carbon and sulfur to express superconductivity at 59 degrees Fahrenheit. Unfortunately, it requires crushing the material between a pair of diamonds at pressures approximately 75% as intense as those in Earth’s core.

While the ultimate utility of high-temperature superconductors will likely not be known for some time, many consider it among the most promising technologies of the 21st century. In a 2018 interview, Bednorz, now retired, explained that IBM’s corporate leadership was integral to the Nobel breakthrough, precisely because the C-suite supported the foundational work without demanding proof of its practicality or immediate payoff: “Oftentimes,” he said, “breakthroughs are made by researchers who think nothing is impossible. You develop ideas and visions when you dream of overcoming fundamental boundaries and being inspired by barriers to understanding.”