Physicists propose new mechanism to enhance superconductivity with 'quantum glue'

A team of researchers, including scientists from HSE MIEM, has demonstrated that defects in a material can enhance, rather than hinder, superconductivity. This occurs through interaction between defective and cleaner regions, which creates a 'quantum glue'—a uniform component that binds distinct superconducting regions into a single network. Calculations confirm that this mechanism could aid in developing superconductors that operate at higher temperatures. The study has been published in Communications Physics.

Superconductivity is a state in which electric current flows through a material without resistance, losing no energy as heat. In ordinary conductors, electrons move independently and lose energy through collisions with atoms and impurities. In superconductors, however, electrons form Cooper pairs and move in unison, enabling current to flow without loss. Thanks to this property, superconductors are used to create powerful magnets, medical MRI scanners, and particle accelerators, and they also hold promise for developing new types of computing devices.

The challenge is that superconductivity usually occurs only at very low temperatures and is easily disrupted by impurities and defects in the material. These defects fragment superconductivity into isolated regions that fail to connect. Paradoxically, however, such disordered areas can also support the formation of Cooper pairs at higher temperatures. This creates a contradiction: structural disorder can locally enhance superconductivity, yet at the same time prevents it from spreading throughout the entire sample.

A team of researchers from HSE University, the Moscow Centre for Advanced Studies, and the Federal University of Pernambuco has shown that this challenge can be addressed by combining defective ('dirty') and clean subsystems. The team studied a two-band model in which one subsystem is highly disordered: superconductivity emerges there at higher temperatures, but only in isolated regions. The other subsystem remains clean, where superconductivity is weaker but provides connectivity. When the two are combined, a component arises that acts as a 'quantum glue,' linking the isolated islands and enabling current to flow through the entire sample at elevated temperatures.

'Our calculations show that when defective and clean regions are properly connected, the material exhibits both a higher superconducting transition temperature and the ability to carry current without resistance. While disorder usually destroys this effect, we observed the opposite: defects can serve as a resource for creating more stable superconductors that operate at higher temperatures,' explains Alexey Vagov, Professor at HSE MIEM and co-author of the study. 

Calculations confirm that this approach is effective for various types of disorder, ranging from random impurities to specially engineered superlattices. It is particularly promising for multilayer materials, where clean and disordered layers can be alternated; for compounds based on magnesium and boron (MgB₂), in which one electronic band enhances local superconductivity while the other facilitates current flow; and for materials with flat electronic bands, where electron pairing occurs more readily. Graphene- and graphite-based systems are also considered promising, as regular superstructures can form that alter electronic properties and promote stronger superconductivity. In the future, this could enable the development of materials in which defects and impurities do not hinder, but rather enhance, superconductivity.

The study was conducted with support from the Russian Science Foundation (Project 075-15-2025-010) and the HSE Basic Research Programme, using the university's HPC cluster.