⚡ A new method to predict high-temperature superconductors

Electricity flows through our cables, but some energy is lost as heat. These losses could be avoided thanks to superconductors: materials capable of carrying current without any resistance.

Researchers at Penn State University have developed a new method to predict which materials could become superconductors, opening the door to applications that would profoundly change our technologies.


Superconductivity has long been explained by BCS theory, which states that electrons pair up (called "Cooper pairs") at very low temperatures to flow without obstruction. But this model only works under extreme cold conditions, close to absolute zero (-459 °F / -273 °C), which limits its practical use. Zi-Kui Liu's team therefore combined two theoretical tools: density functional theory (DFT), which simulates electron behavior, and zentropy theory, which describes how a material transitions from the superconducting state to the normal state.

DFT makes it possible to predict a material's electronic properties through computation, without the need for costly experiments. By observing electron density, researchers can detect configurations that resemble those of Cooper pairs, but at higher temperatures. Using this approach, they identified superconducting behaviors in metals such as copper, silver, and gold, which were not previously considered superconductors.

Zentropy theory, on the other hand, combines quantum physics and statistical mechanics to understand how a material loses its superconductivity with temperature. It notably allows estimation of the critical transition temperature, an essential parameter if we want to use these materials in everyday life. The goal now is to apply this method to a vast database of materials to identify new promising candidates.

Next steps include predicting material behavior under different pressures and testing them in the laboratory. If these predictions are confirmed, they could lead to the discovery of superconductors that operate at high temperatures, or even at room temperature. Such an advance would transform how we produce, transport, and use electricity.

Zi-Kui Liu summarizes the challenge: it is not just about explaining what we already know, but about building a theoretical framework to discover the unknown. By connecting several previously separate theories, his team opens new perspectives toward more efficient and sustainable energy.

BCS Theory and Cooper Pairs

BCS theory, proposed by John Bardeen, Leon Cooper, and John Schrieffer, describes low-temperature superconductivity. It explains that electrons do not travel alone but in pairs, the "Cooper pairs". These pairs move together through the crystal lattice without colliding with atoms, which eliminates electrical resistance.

But these pairs are fragile and break apart as soon as the temperature rises. This is why conventional superconductors only work at very low temperatures, achieved with expensive cooling systems. This model fails to explain so-called "unconventional" superconductivity, discovered in families of materials such as cuprates.

Density Functional Theory (DFT)

DFT is a computational method in quantum mechanics that makes it possible to predict the properties of a system based on electron density rather than complex wave function equations.

Developed in the 1960s, it has become an essential tool for chemistry and materials science, as it enables reliable predictions with reasonable computing resources.

In the case of superconductors, DFT does not directly describe the formation of Cooper pairs, but it can reveal clues to behaviors favorable to superconductivity. By combining it with other models such as zentropy, it allows faster exploration of complex phenomena and identification of potentially revolutionary materials.