A team of theorists has shown that the redistribution of electrons in the layers of copper and oxygen atoms is governed by the proximity to a metal-insulator transition.

Layer of CuO2

Cuprates are high-temperature superconducting materials with strong potential for applications in advanced quantum technologies. Understanding how the electrons are redistributed between copper and oxygen in the conducting planes of the cuprates is at the hearth of the high-temperature superconductivity problem.

Now, a team of theoretical physicists at Royal Holloway (master’s student Gemma Reaney and Dr. Giovanni Sordi) and at Université de Sherbrooke in Canada (Nicolas Kowalski and Prof. André-Marie Tremblay) have shown in modelling simulations that the position of the cuprates, relative to the boundary between a correlated insulator and a metal, controls this electronic redistribution.

This result was obtained through a comprehensive study of the phase diagram of the normal state of a quantum mechanical model known as Emery model, using state-of-the-art and computationally intensive calculations based on advanced theoretical methods. The findings of the work identify the drivers of the microscopic process of this charge redistribution and offer an approach for understanding observed experimental trends in cuprates.

Article: G. L. Reaney, N. Kowalski, A.-M. S. Tremblay, and G. Sordi, Charge gap and charge redistribution among copper and oxygen orbitals in the normal state of the Emery model, Phys. Rev. B 112, 125106 (2025)
https://doi.org/10.1103/7bbg-m38l