Novel Transition-Metal Oxides Under Pressure

Transition-metal oxides have been the focus of multiple experimental and theoretical research efforts because of their versatility and applicability to new technology. These characteristics mostly owe to our ability to adjust valence states and crystal fields, among others, by fine-tuning thermodynamic variables. From this tuning, interesting and sometimes competing properties emerge; but it is often necessary to take these oxides to extremes conditions of pressure, temperature or magnetic field so novel phenomena arise (e.g. P ∼100 GPa = 1 Mbar, T ∼1 K, µ0H ∼10 T), which is the case for some high-temperature superconductors and Kitaev quantum spin liquids (KQSLs). In particular, the latter is a frustrated state of matter, modeled for 2D honeycomb lattices, that hosts topologically protected excitations and presents immense potential for application to fault-tolerant quantum computing. However, reliable stabilization of this state in real materials has been challenging. Therefore, this work aimed at unraveling atomic, electronic and magnetic structures of KQSL-candidate Na3Co2SbO6 at thermodynamic extremes, by combining multiple techniques and diamond anvil cells. Na3Co2SbO6 shows no structural dimerization up to 1 Mbar, likely due to the reduced spatial extent of Co 3d orbitals compared to Rh 4d and Ir 5d bands in other Kitaev candidates. Pressure suppresses this cobaltate’s magnetic response, which vanishes above 100 GPa in good agreement with induced frustration. Although a high-to-low-spin transition at ∼70 GPa quenches the orbital momentum required in KQSLs, other models predict that honeycomb lattices of low-spin Co2+ ions can host a spin-liquid phase, which is of great interest for related research. Contributions to the study of another Kitaev-candidate material, Ag3LiRh2O6, are also highlighted. Furthermore, superconducting transitions were explored on nickelates. For the first time, a temperature-dependent resistivity drop was reported for compressed Pr4Ni3O10, suggesting that bulk superconductivity is a more general property of Ruddlesden-Popper Ni-O stacks under pressure.

Author dc:creator

• Eduardo Henrique de Toledo Poldi (23291365)

• Physics
• Condensed Matter

Statement dc:rights

• In Copyright

DOI dc:identifier

https://doi.org/10.25417/uic.31451116.v1

OAI identifier oai:identifier

oai:figshare.com:article/31451116