Pressure-induced dimensional crossover in RuBr3 and RuI3

We will study pressure-induced structural transformations in RuBr3 and RuI3, the new van der Waals magnets. At ambient pressure, these compounds form chain-like structures where short Ru-Ru bonds prevent the Ru3+ ions from being magnetic. A high-pressure high-temperature treatment transforms both compounds into layered and magnetic polymorphs that are promising hosts for the Kitaev spin liquid and other exotic quantum phenomena. We seek to study details of this transformation by high-pressure x-ray diffraction. We will map out the different polymorphs of RuBr3 and RuI3 and their stability range as a function of pressure and temperature. This will help us to determine the pressure region where Ru3+ retains its magnetism. We will also establish optimal conditions for the synthesis of magnetic polymorphs of RuBr3 and RuI3. Our study will contribute to the knowledge of pressure-induced transformations and dimensional crossover in transition-metal trihalides as van der Waals magnets.