Seminarium Fizyki Materii Skondensowanej

The definition of variational wave functions represents an invaluable tool to describe strongly-correlated systems. A promising playground where this kind of approach has been fruitfully applied lies in highly-frustrated spin models, where spin-liquid phases may emerge from the competition of various super-exchange interactions. Gutzwiller-projected wave functions (constructed from fermionic and bosonic constituents) have been employed since the pioneering suggestion by Anderson of the resonating-valence-bond theory. In the recent years, we demonstrated that the fermionic approach gives very accurate results for simple Heisenberg models with SU(2) spin symmetry. The next challenge is now to incorporate further ingredients in the microscopic Hamiltonians. Examples are given by the inclusion of the Dzyaloshinskii-Moriya interaction (or, more generally, anisotropic-exchange couplings, as present in Kitaev materials) or quantum phonons. Besides being relevant for an accurate description of real materials, these additional perturbations are extremely useful to assess the stability of spin-liquid phases, especially the gapless ones. In this talk, we discuss the accuracy of Gutzwiller-projected wave functions to determine the correct results of these extended models.