Phase diagrams and neutron scattering spectra of triangular lattice antiferromagnets from theory and matrix product state computations

Ever since the pioneering work of Anderson, the possibility of exotic magnetic phases on the triangular lattice has attracted interest.  Phase diagrams for spin and Hubbard models are presented, together with intuitive explanations where those are available.  We then turn to recent advances in the ability to predict inelastric neutron scattering spectra by dynamical calculations using matrix product state methods.  While computational methods for frustrated two-dimensional quantum magnets are still evolving, they are able to provide relatively unbiased approximate spectra for comparison to experiment, as demonstrated for materials in the YbSe2 and YbZnGaO families.  Neutron scattering results on these materials are shown to be consistent with predicted spectra for various points in the phase diagram of the anisotropic J1-J2 model, near the boundary between a Dirac spin liquid and conventional three-sublattice order.  We close with a discussion of the implications for theory and applications of finding either chiral spin liquids or U(1) Dirac quantum spin liquids on the triangular lattice.

The work presented resulted from theoretical collaborations with Berkeley colleagues T. Cookmeyer, J. Motruk, N. Sherman, A. Szasz, K. Wang, and M. Zaletel, and experimental collaborations with groups led by S. Haravifard, A. Scheie, and A. Tennant.