Critical phenomena around the SU(3) symmetric tri-critical point of a spin-1 chain

We investigate critical phenomena of a spin-1 chain in the vicinity of the SU(3) symmetric critical point, which we already specified in the previous study. We numerically diagonalize a Hamiltonian combining the bilinear-biquadratic (BLBQ) Hamiltonian with the trimer Hamiltonian. We then discuss the numerical results based on the conformal field theory (CFT) and the renormalization group. As a result, we firstly verify that the critical point found in our previous study is the tri-critical point among the Haldane phase, trimer phase, and the trimer liquid (TL) phase. Secondly, with regard to the TL–trimer transition and TL–Haldane transition, we find that the critical phenomena around this tri-critical point belong to the Berezinskii–Kosterlitz–Thouless (BKT)-like universality class. We thirdly find the boundary between the Haldane phase and the trimer phase, which is illustrated by the massive self-dual sine-Gordon (SDSG) model.