SPICE Workshop on Quantum Matter for Quantum Technologies, May 21st - May 23rd 2024
Floriana Lombardi
The properties of the cuprates superconductors are strongly dependent on chemical/oxygen doping; yet, the very complex stoichiometry makes it impossible to disentangle the effect of doping, on the electronic system, from the variations in crystalline structure. Despite recent successes using strain and pressure to change some of the properties of the material, the cuprates remain very marginally tunable. This represents a major obstacle to disentangle the various correlated electronic phase contributing to the physics of these materials.
In this contribution we present a novel approach that uses the unique morphology of substrates as a novel tuning parameter to drastically alter the cuprate’s properties. By engineering nanofaceted surfaces, additional substrate potentials are created, capable of modifying the Fermi surface and influencing the various phases within the cuprate phase diagram, such as the strange metal and Charge Density Wave (CDW) phases. The transport properties of ultrathin and underdoped YBCO thin films show remarkable new findings. The Fermi surface transforms into a nematic state which suppress the CDW, as detected by Resonant Inelastic X-ray scattering. This leads to a T-linear resistivity, in the strange metal phase of the films, extending down to the superconductive transition temperature, mirroring behaviors only observed in optimally doped single crystals. These observations hint at a profound connection between the onset of the CDW and the departure from strange metal behavior in underdoped cuprates. Moreover, the study reveals significant enhancements in superconducting critical temperature and upper critical field in ultrathin films compared to single crystals, that we attribute to the nematic Fermi surface. Overall, these findings open up new avenues for manipulating the cuprate ground states by precisely nanopatterning the substrate surfaces, thus generating different substrate potential geometries and symmetries. This research not only sheds light on the fundamental physics of cuprate superconductors but also offers promising prospects for advancing their practical applications.