Structural, Electronic and Magnetic Instabilities in Candidate Quantum Spin Liquid Honeycomb Iridates

It has long been recognized that in a spin system a paramagnetic ground state could be induced by strong quantum fluctuations, that are able to inhibit the long range magnetic ordering. A special class of quantum paramagnets is represented by the so-called Quantum Spin Liquids (QSLs), in which spins are highly correlated and still fluctuate at T=0K. This behavior occurs in presence of large degeneracy in the system ground state, which can be due to frustration. Among promising QSL materials, honeycomb iridates are getting more and more attention in the latest years. Despite the first candidate QSL iridates Li2IrO3 and Na2IrO3 were experimentally found to order magnetically at low temperatures, the recently synthesized H3LiIr2O6 does not show any magnetic ordering down to 1K. To clarify the reasons why a QSL behavior can be stabilized in H3LiIr2O6, a deep understanding of all the aforementioned iridates is necessary. Therefore, we perform ab-initio DFT and DFT+U calculations using QUANTUM ESPRESSO and VASP, focusing first on the structure of these materials and then on their magnetic and electronic properties, looking for the occurrence of instabilities that could inhibit the QSL state.