In-plane anisotropic ground states are ubiquitous in correlated solids such as pnictides, cuprates and manganites. They can arise from doping Mott insulators and compete with phases such as superconductivity, however their origins are debated. Strong
coupling between lattice, charge, orbital and spin degrees of freedom results in simultaneous ordering of multiple parameters, masking the mechanism that drives the transition. We demonstrate that the anisotropic orbital domains in a manganite can be oriented by the polarization of a pulsed THz light field. Through the application of the Hubbard model, we show that domain control can be achieved either through field assisted hopping of charges or a field-induced modification of bond angles. Both routes enhance the local Coulomb repulsions which drive domain reorientation and the dominant mechanism is dictated by the equilibrium Mn-O-Mn bond angle. Our results highlight the key role played by the Coulomb interaction in driving orbital order in manganites and demonstrate how THz can be utilized in new ways to understand and manipulate anisotropic phases in a broad range of correlated materials.
We study the Mott phase of three-component bosons, with one particle per site, in an optical lattice by mapping it onto an SU(3) spin model. In the simplest case of full SU(3) symmetry, one obtains a ferromagnetic Heisenberg model. Introducing an SU(
3) analog of spin-orbit coupling, additional spin-spin interactions are generated. We first consider the scenario of spin-dependent hopping phases, leading to Dzyaloshinskii-Moriya-type interactions. They result in the formation of spiral spin textures, which in one dimension can be understood by a local unitary transformation. Applying classical Monte Carlo simulations, we extend our study to two-dimensional systems, and systems with true spin-orbit coupling, involving spin-changing hoppings.
