Programma: PRIN
Responsabile scientifico per il dipartimento: Samuele Sanna
Struttura principale: DIFA
Data inizio e data fine: dal 28/09/2023 al 28/09/2025
Ossidi di osmio: nuovi orizzonti nei materiali quantistici
Il progetto esplora i perovskiti Ba₂MOsO₆, Dirac-Mott insulator con forti correlazioni elettroniche e spin-orbita, per comprendere transizioni magnetiche e strutturali tramite tecniche sperimentali e teoriche.
Osmium Oxides: New Frontiers in Quantum Materials
The project investigates Ba₂MOsO₆ perovskites, Dirac-Mott insulators with strong electronic correlations and spin-orbit coupling, to understand magnetic and structural transitions via theory and experiments.
Abstract
The combined effect of strong electronic correlations with spin-orbit coupling generates emergent quantum phenomena which arestill poorly explored or unclear. Their study represents a central issue in quantum materials research. In perovskites containing 5dtransition metal ions the interplay between orbital, spin and charge degrees of freedom gives rise to exotic magnetic states.Osmates double perovskites emerged as one of the most interesting realizations of this rich phenomenology and offer a uniqueenvironment to study it. The peculiarity of these systems resides in the simultaneous presence of strong spin-orbit interaction andsizeable electronic correlation: this dictates the fate of these would-be metals where the electronic correlation is enhanced by therelativistic spin-orbit coupling with the consequent formation of a Mott insulating ground state. For this reason they are known asrelativistic or Dirac-Mott insulators [1].The sizable spin-orbit interaction and the ligand field have a second important consequence: the presence of a strong connectionbetween the electronic properties of these systems and their crystal structure. Finally, the similar energy scales of spin-orbitinteraction and electronic correlation leads to strong responses to external stimuli, such as electric and magnetic fields, physical andchemical pressure, strain and doping. This results in a plethora of unconventional properties whose exploration, understanding, and,above all, exploitation is definitely missing.The present project is devoted to the study of one of the most representative members of the Dirac-Mott insulators, Ba2MOsO6 (withM diamagnetic ions), whose magnetic behavior depends dramatically on the M ion. The choice of M influences the electronicoccupation of 5d orbitals and directly affects the charge and structural degrees of freedom. This may lead to a transition from a(canted) antiferromagnetic-like quadrupolar ground state, suggested to be triggered by a local Jahn-Teller distortions, to possibly acollinear antiferromagnetic or a multipolar order, still under debate. Our proposal is to finely tune the structural and charge degreesof freedom with applied and chemical pressure or with charge chemical doping, obtained with partial isovalent or heterovalentsubstitutions in the M site, and to explore the magnetic and structural phase diagram of this system acting on well controlledparameters.We will make use of two local probe techniques, nuclear magnetic/quadrupolar resonance and muon spin spectroscopy, that provedto be extremely effective in the identification of the details of magnetic and structural transitions and also in case of multipolar orderand subtle local distortions. We will properly combine this experimental investigation with computational support aiming at providingan accurate interpretation of the observed phenomenology, which remains a challenging topic both from theoretical andexperimental sides.