2D superconductivity in cuprate oxychlorides
Lorenzo Menon¹, Dario Daghero², Pierre Rodière¹, Erik Piatti², Renato Gonnelli² and Matteo d'Astuto^1
1CNRS, Institut Néel, Grenoble, France
²Dipartimento di Fisica, Politecnico di Torino, Torino, Italy

Despite decades of research effort, the origin of high temperature superconductivity in cuprates remains one of the most challenging questions in condensed matter physics, particularly regarding its interplay with competing electronic phases such as antiferromagnetism, charge order, and the pseudogap state. In this context, the hole-doped cuprate oxychloride Ca_2-xNa_xCuO₂Cl₂ (Na-CCOC), offers a promising playground to investigate all three phases, due to its simple crystal structure, with a simple crystal structure stable over a wide doping range, and strong two-dimensional character.
Recent studies revealed an unusual superconducting anisotropy in this compoun, possibly linked to pair-density waves or an intrinsically two-dimensional electronic structure, a scenario that would enable the study of 2D superconductivity in bulk materials.

Our project aims to quantify this anisotropy and understand its origin and interplay with other electronic phases, in particular by investigating the possible intrinsic two-dimensional character of the superconductivity and its symmetry. To address these questions, we combine structural, magnetic, transport and spectroscopic techniques.
​​​​​​​Crystallography is used to clarify the role of crystal mosaicity and disorder, while magnetization and transport measurements probe the electronic response. In particular, high-resolution Tunnel Diode Oscillator (TDO) measurements, as a high-frequency magnetization technique, are employed to investigate the evolution of the magnetic penetration depth and the superfluid density. Spectroscopic techniques provide important complementary information: point-contact spectroscopy (PCS) probes the amplitude and symmetry of the superconducting gap, while angle-resolved photoemission spectroscopy (ARPES) gives access to key aspects of the electronic structure.

First measurements have been carried out for each of these techniques, yielding preliminary results that are currently under analysis.