Cuprate Model Shows Spin Susceptibility Onset Temperature Tracks Critical Temperature of High-Temperature Superconductors

Understanding the origins of high-temperature superconductivity remains a central challenge in condensed matter physics, and recent work by Keishichiro Tanaka investigates the magnetic properties of materials that closely resemble these superconductors. This research explores how the tendency of electrons to align their spins, known as spin susceptibility, changes with temperature in a model cuprate material exhibiting a ‘pseudogap’, a key feature of high-temperature superconductors. The results demonstrate that the temperature at which this spin alignment begins closely matches the critical temperature for superconductivity, suggesting a strong link between magnetism and the ability of these materials to conduct electricity without resistance. Furthermore, the study reveals that as the material’s electron density decreases, the spin susceptibility increases significantly, indicating that suppressing these magnetic fluctuations may be crucial for achieving superconductivity and preventing the disruption of electron pairing.

Scientists measured how easily the material responds to a magnetic field, known as spin susceptibility, at specific points representing electronic momentum, and found a strong connection to the temperature at which superconductivity appears. The team focused on a model material exhibiting characteristics similar to cuprates, including an ‘antinodal pseudogap’, a region of suppressed electronic behaviour.

Cluster Dynamical Mean-Field Theory Simulations of Correlations

This study employs advanced theoretical and computational techniques, specifically Cluster Dynamical Mean-Field Theory (CDMFT), to investigate the electronic properties of materials. CDMFT combines the advantages of capturing both local and non-local electronic interactions, providing a powerful method for understanding strongly correlated electron systems. The research aims to go beyond traditional theories that struggle to accurately describe materials where electrons strongly influence each other. The team validated their calculations by demonstrating the equivalence between two different methods for calculating the system’s response to external influences, ensuring the accuracy and reliability of their results. This research framework has broad applications, including understanding high-temperature superconductors, Mott insulators, and other materials with complex electronic properties.

Spin Susceptibility Tracks Superconducting Onset Temperature

This research delivers a detailed understanding of spin susceptibility in a model cuprate material, crucial for unraveling the mechanisms behind high-temperature superconductivity. Measurements confirm that the temperature at which susceptibility begins to increase closely matches the critical temperature for superconductivity. The team evaluated both a simplified and a more refined calculation of susceptibility to extract this onset temperature. Results demonstrate that decreasing the number of electrons in the material enhances the susceptibility, particularly at a specific momentum point representing an axial particle-hole response.

Further analysis reveals that the emergence of superconductivity correlates with a suppression of low-energy spin responses and associated particle-hole excitations. This suppression is critical, as these excitations would otherwise disrupt the formation of d-wave pairing, a key characteristic of these superconductors. The pseudogap, a fundamental feature of these materials, partially suppresses spectral weight near zero energy, effectively reducing the available phase space for these disruptive excitations. This work establishes a clear link between the pseudogap, spin susceptibility, and the emergence of superconductivity, providing valuable insights into the complex interplay of electronic interactions within these materials.

Spin Susceptibility Links to Superconductivity Emergence

This research presents detailed calculations of spin susceptibility in a model system designed to mimic the behaviour of high-temperature superconducting cuprates, particularly focusing on the role of the antinodal pseudogap. The results demonstrate a strong correlation between the temperature at which susceptibility begins to increase and the critical temperature for superconductivity in these materials, suggesting a shared underlying mechanism. Importantly, the findings suggest that as the number of electrons decreases, the susceptibility grows significantly, indicating an enhanced response within the material. The research suggests that the emergence of superconductivity is linked to the suppression of spin responses and associated particle-hole excitations, which could otherwise disrupt the pairing of electrons responsible for superconductivity. The pseudogap, a characteristic feature of these materials, appears to partially suppress these disruptive excitations, effectively creating more favourable conditions for superconductivity. While the calculations are based on a specific model system, the research provides valuable insights into the fundamental physics governing high-temperature superconductivity and highlights the importance of the antinodal region in controlling material properties.