Quenched disorder in frustrated quantum magnets

4 problems

• Is $\mathrm{H_3LiIr_2O_6}$ a bond-disordered Kitaev spin liquid?

  Contested

  $\mathrm{H_3LiIr_2O_6}$ is a honeycomb iridium oxide that shows no magnetic order down to the lowest temperatures measured. The hydrogen atoms between its layers are disordered, and it is unclear whether its state is a Kitaev spin liquid altered by random couplings or a collection of random spin pairs unrelated to Kitaev physics.

• Is the 2D random-singlet state one phase with finite dynamic exponent?

  Open

  In one dimension, random couplings produce the random-singlet state, where spins pair at all distances and time scales grow exponentially with length. Simulations in two dimensions find a similar pairing state with time scales growing only as a power of length, and whether it is one universal phase is unclear.

• Origin of universal H/T scaling in disordered frustrated magnets

  Open

  In several frustrated magnets with chemical disorder, heat capacity and magnetization measured at many fields and temperatures fall onto one curve when plotted against field divided by temperature. The collapse points to a common population of weakly bound spin pairs, but no microscopic theory has yet predicted the exponent for a specific material.

• Is $\mathrm{YbMgGaO_4}$ a spin liquid or a disorder-driven state?

  Contested

  $\mathrm{YbMgGaO_4}$ is a triangular-lattice magnet with no detected order and a broad continuum of spin excitations, first read as a spin-liquid signature. Its magnesium and gallium atoms are randomly mixed, which makes the couplings random, and that alone may produce the same data.