Speaker
Description
Ruddlesden-Popper (RP) nickelates have recently attracted significant attention following the emergence of superconductivity under pressure. However, their interpretation is often complicated by phase intergrowth and oxygen non-stoichiometry in crystals grown by the optical floating-zone method. Reliable identification of the structural phase is therefore essential prior to spectroscopic, transport, or thermodynamic investigations. Here, we show that polarization-resolved Raman spectroscopy provides a rapid and sensitive probe for phase identification in RP nickelates. By systematically characterizing monolayer, bilayer, monolayer–trilayer polymorph, and trilayer compounds, we establish distinct spectral fingerprints that enable unambiguous discrimination between different RP members and their polymorphs, while also allowing assessment of sample quality in the presence of mixed phases.
In addition, we present the development of a high-pressure AC susceptibility setup employing a gasket-integrated coil design to probe the Meissner response of micron-scale samples inside a diamond anvil cell. Detecting superconductivity in nickelates is particularly challenging because of the small sample volume and the reported low superconducting volume fractions, in some cases below 1%, requiring substantial improvements in signal-to-noise ratio. The setup enables reproducible measurements without repeated coil fabrication or rewiring, thereby significantly reducing experimental overhead.
These developments establish a practical route toward reliable phase identification and quantitative probing of superconductivity in nickelates, providing a versatile platform for studying correlated materials under extreme conditions.