| An insightful review paper presents detailed studies by LPS physicists on the impact of impurities and disorder on the electronic properties of high-Tc superconducting cuprates. These findings reflect the culmination of longstanding, collaborative research efforts by LPS scientists and their collaborators, capturing decades of investigation into the complexities of these materials. |
For years, LPS researchers and their collaborators have conducted in-depth investigations into the effects of impurities and disorder on the electronic properties of high-Tc superconducting cuprates. Their findings show that in minimally disordered YBa₂Cu₃O6+x, introducing spinless impurities such as Zn or Li at planar Cu sites effectively tunes the boundaries of both the spin glass phase and the superconducting dome. NMR data indicate that these defects create a surrounding cloud exhibiting Kondo-like paramagnetic behavior, with notable differences between the pseudogap and strange metal phases.
Furthermore, the researchers investigated the evolution of transport properties with the disorder by the introduction of a controlled content of in-plane vacancies by electron irradiation. At high T the inelastic scattering of the carriers is surprisingly disorder-independent, and governed by the excitations of the correlated electronic state. The low T upturns of the resistivity, that are associated with single impurity Kondo-like scattering, agree qualitatively with the local magnetism induced by spin-less impurities. Very large defect contents are required to induce Metal Insulator Crossovers.
In the Superconducting state, the defect-induced reduction of Tc scales quasi linearly with residual resistivity. The paraconductivity due to the superconducting fluctuations, deduced from high field magnetoresistance measurements vanishes beyond a temperature T’c and a field H’c that decrease with increasing defect content.
In the pseudogap regime the weaker decrease of T’c with respect to that of Tc reveals a loss of superconductivity phase coherence in the presence of disorder. This initiates a discussion of its interplay with pair breaking and allows one to confirm that the family specific dopant induced disorder or order controls the phase diagram. In the ideal disorder free cuprate the 2D Superconducting state would certainly persist at low doping.
This collection of data presents significant challenges to the theoretical understanding of the superconducting and normal states in these correlated electron systems. All of these findings, along with further discussion, are detailed in the review article recently published in Frontiers in Physics.
Contributors
Spectroscopie des Matériaux Quantiques au LPS (RMN avec Julien Bobroff and Philippe Mendels)
SPEC-CEA, Orme des Merisiers, Saclay (Transport électronique avec Florence Rullier-Albenque)
Irradiations électroniques au LSI (Ecole Polytechnique) Mesures en champ intenses au LCMI (Toulouse).
Fundings
LabEx PALM
References
Henri Alloul, “What do we learn from impurities and disorder in High Tc cuprates?”
Front. Phys. 12:1406242 (2024) doi: 10.3389/fphy.2024.1406242
Contacts
Henri Alloul – henri.alloul@universite-paris-saclay.fr