Are room-temperature superconductors finally within reach?

The Challenge of Cold Superconductors

Despite their promise, most superconducting materials cannot yet be used in everyday technology. Their extraordinary ability to conduct electricity only appears at extremely low temperatures, far below what is practical for energy systems or advanced electronics. Supported by the "Theory of Condensed Matter" program within the Department of Energy's (DOE) Basic Energy Sciences, the Penn State team created a new computational approach to predict which materials might display superconductivity, potentially paving the way to finding ones that work at much higher, even near-room, temperatures.

A New Look at a Longstanding Mystery

Predicting superconductivity -- especially in materials that could operate at higher temperatures -- has remained an unsolved challenge. Existing theories have long been considered accurate only for low-temperature superconductors, explained Zi-Kui Liu, a professor of materials science and engineering at Penn State.

"The goal has always been to raise the temperature at which superconductivity persists," said Liu, the lead author of a new study published in Superconductor Science and Technology. "But first, we need to understand exactly how superconductivity happens, and that is where our work comes in."

How the Classic Theory Explains Superconductors

For decades, scientists have relied on the Bardeen-Cooper-Schrieffer (BCS) theory to describe how conventional superconductors function at extremely low temperatures. According to this theory, electrons move without resistance because of interactions with vibrations in the atomic lattice, called phonons. These interactions allow electrons to pair up into what are known as Cooper pairs, which move in sync through the material, avoiding atomic collisions and preventing energy loss as heat.

"Imagine a superhighway just for electrons," Liu explained. "If there are too many routes, electrons bump into things and lose energy. But if you create a straight tunnel for them, like the Autobahn in Germany, they can travel fast and freely without resistance."

The Quest for Power Without Resistance

This ability to transmit energy without resistance is what makes superconductors so promising, Liu said. If scientists can develop materials that stay superconducting at higher temperatures, electricity could travel farther, faster, and more efficiently, transforming global power systems. To understand this phenomenon, the DOE-backed project uses computational tools known as density functional theory (DFT). DFT helps model how electrons behave in ordinary conductors compared to superconductors. The team hypothesizes that even though DFT does not directly model Cooper pairs, the electron density it predicts should resemble that of paired electrons, allowing researchers to study potential superconducting behavior.

Until recently, BCS theory and DFT -- one describing electron pairing, the other rooted in quantum mechanics -- were treated separately. Liu's team found a way to connect these frameworks, creating a new path to predict superconductivity.

Introducing Zentropy Theory

The breakthrough centers on a concept called zentropy theory. This approach merges principles from statistical mechanics, which studies the collective behavior of many particles, with quantum physics and modern computational modeling. Zentropy theory links a material's electronic structure to how its properties change with temperature, revealing when it transitions from a superconducting to a non-superconducting state. To apply the theory, scientists must understand how a material behaves at absolute zero (zero Kelvin), the coldest temperature possible, where all atomic motion ceases. Liu's team demonstrated that even DFT -- though not originally intended to study superconductors -- can provide key insights into when and how superconductivity occurs.

Predicting the Next Generation of Superconductors

According to Liu, the new method allows scientists to predict whether a material could become superconducting. Zentropy theory can then estimate the critical temperature at which the material loses that property. The classic BCS theory successfully explains superconductors that operate only at very low temperatures, but fails for high-temperature varieties, where Cooper pairs break apart more easily. Through DFT modeling, Liu's group discovered that in high-temperature superconductors, the electron "superhighway" remains stable because of a unique atomic structure -- similar to a pontoon bridge that flexes with waves, allowing electrons to move smoothly even when thermal vibrations increase.

Using this combined approach, the team successfully predicted superconducting behavior in both conventional and high-temperature materials, including one that traditional theory could not explain. They also forecasted potential superconductivity in copper, silver, and gold -- metals not typically considered superconductors -- likely because they would require extremely low temperatures for the effect to appear. These findings could accelerate the discovery of new materials that operate as superconductors at higher, more practical temperatures.

Next Steps in the Search for Practical Superconductors

The Penn State researchers now plan to expand their work in two ways. First, they will use the zentropy theory to predict how pressure affects the temperature at which superconductors lose their resistance. Second, they will search a massive database of five million materials to identify new candidates that could exhibit superconductivity. The goal is to find the most promising materials and collaborate with experimental researchers to test them.

"We are not just explaining what is already known," Liu said. "We are building a framework to discover something entirely new. If successful, the approach could lead to the discovery of high-temperature superconductors that work in practical settings, potentially even at room temperature if they exist. That kind of breakthrough could have an enormous impact on modern technology and energy systems."

Shun-Li Shang, research professor of materials science and engineering at Penn State, is a co-investigator on this study.

The U.S. Department of Energy supported this research.