Recently there has been considerable excitement surrounding the promising realization of high-spin Kitaev material, such as the quasi-2D compound CrI
3 and CrGeTe
3. However, the stability of quantum spin liquids (QSL) against single ion anisotropy (SIA) in these materials and the global quantum phase diagram of the extended spin-3/2 Kitaev model with finite SIA remain unclear. In this study, we perform large-scale density matrix renormalization group (DMRG) to explore the quantum phase diagram of the generalized spin-3/2 Kitaev-Heisenberg (K-H) model accompanied with SIA
Ac. In the
Ac=0 limit, the spin-3/2 K-H model exhibits a quantum phase diagram similar to that of a spin-1/2 system, including two QSLs around antiferromagnetic and ferromagnetic Kitaev models. For models with finite
Ac, we map out the quantum phase diagram around two Kitaev points and observe distinct types of in-plane vortex orders developed from these two QSL phases. Interestingly, series of nearly degenerate vortex configurations are discovered in each vortex phases. Using linear spin-wave theory, we demonstrate that these vortex configurations can be understood as a consequence of the quantum correction on a continuous family of degenerate classical states.
From known phase diagram regions of different model Hamiltonians describing strongly correlated systems we deduced new domains of the ground state phase diagram of the same models by a unitary transformation. Different types of extended Hubbard Hamiltonians were used for the starting point and the existence of new stable spin-density waves, charge-density waves, ferromagnetic states and a paramagnetic insulator is demonstrated. The procedure used is dimension independent. The ground state phase diagrams of several strongly correlated systems modelled by extended Hubbard-like Hamiltonians are analysed using unitary transformations. New stable spin-density wave, charge-density wave, ferromagnetic or paramagnetic insulator phases are obtained in different cases. The results are true in any dimensions. SUMMARY In this paper, we have presented a procedure based on an explicitly given unitary transformation which allows the rigorous deduction of new phase diagram domains starting from known ground state solutions of a given model. The method is not model dependent and can be applied for arbitrary dimensions. We have applied this method to find new stable spin-density wave, charge-density wave, ferromagnetic and paramagnetic insulator domains of different extended Hubbard type models.
We study the extended Kitaev-Heisenberg (EKH) quantum spin model by adding bond-dependent off-diagonal Heisenberg term into the original KH model, which was recently proposed to describe the honeycomb Iridates. A rigorous mathematical mapping of spin operators reveals the intrinsic symmetry of the model Hamiltonian. By employing an unbiased numerical entanglement renormalization method based on tensor network ansatz, we obtain the global phase diagram containing eight distinct quantum phases. By using the dual mapping of spin operators, each of the individual magnetic phase in the global phase diagram can be clearly understood. At last, we show that a valence solid state emerges as the ground state in the quadro-critical region where multiple magnetic phases compete most intensively.