Theory of competing charge density wave, Kekule, and antiferromagnetically ordered fractional quantum Hall states in graphene aligned with boron nitride

We investigate spin- and valley-symmetry-broken fractional quantum Hall phases within a formalism that naturally extends the paradigm of quantum Hall ferromagnetism from integer to fractional quantum Hall states, allowing us to construct detailed phase diagrams for a large class of multicomponent states. Motivated by recent experiments on graphene aligned with a boron nitride substrate, we predict a sequence of transitions realized by increasing the magnetic field, starting from a sublattice polarized state to a valley coherent Kekule charge density wave state and further to an antiferromagnetic phase. Moreover, for filling fractions such as nu = +/- 1/3, we predict that the system undergoes a transition at low fields, that not only differ by the spin-valley orientation of the fractionally filled flavors, but also by their intrinsic fractional quantum Hall nature. This transition is from a Laughlin-type state to a two-component Halperin-type state both with a charge density wave order. Moreover, for nu = +/- 1/3,+/- 2/3, we predict a canted Kekule density phase where the spinors of integer and fractionally occupied components have different orientations in the valley Bloch sphere, in contrast to the Kekule state for the integer quantum Hall state at neutrality where both occupied components have the same orientation in the valley Bloch sphere.

Automated summary

We investigate spin- and valley-symmetry-broken fractional quantum Hall phases and predict a sequence of transitions from a sublattice polarized state to a valley coherent Kekule charge density wave state and further to an antiferromagnetic phase. For filling fractions such as nu = +/- 1/3, we predict a transition from a Laughlin-type state to a two-component Halperin-type state both with a charge density wave order. Moreover, for nu = +/- 1/3,+/- 2/3, we predict a canted Kekule density phase where the spinors of integer and fractionally occupied components have different orientations in the valley Bloch sphere.