Neel to spin-Peierls transition in the ground and excited state of a quasi-1D Heisenberg model coupled to bond phonons.

The spin-Peierls transtion in the ground state (quantum phase transition) and excited state(thermal phase transition) of a quasi-1D Heisenberg model is investigated using the stochastic series expansion quantum monte carlo method. The transition from a gapless Neel state to a spin-gapped Peierls state is studied in the parameter space spanned by spatial anisotropy, inter-chain coupling and spin-lattice coupling. It is found that for any inter-chain coupling, the transition to a dimerized Peierls state only occurs when the spin-lattice coupling exceeds a finite, non-zero critical value.Bachelor of Science in Physic