Speaker
Description
In the Hamiltonian formulation, free spin-1/2 massless Dirac fermions on a bipartite lattice have an $O(4)$ (spin-charge) symmetry. Lattice interaction terms usually break this symmetry down to some subgroups. For example, the Hubbard interaction at half-filling breaks the symmetry down to $SO(4)$ by breaking the spin-charge flip symmetry. In this work, we construct a lattice model with a new interaction $V$, which is similar to the Hubbard interaction, but preserves the spin-charge flip symmetry. Using perturbative calculations in the continuum, we compute the RG flow diagram with both $U$ and $V$ interactions and show the existence of a spin-charge flip symmetric fixed point that can be studied by tuning the coupling $V$ at $U=0$. In particular we show that this fixed point is different from the one reached by tuning the Hubbard coupling $U$. Monte Carlo calculations using the fermion bag idea can help us compute the critical exponents at the spin-charge flip symmetric fixed point.
