Field induced phase transition in one dimensional Heisenberg antiferromagnet model studed using density matrix renormalization group

Speaker: Peter Gustainis, Affleck group, UBC
Date & Time: Fri, 2017-03-31 13:00 - 14:00
Location: Hennings 309
Local Contact: Ian Affleck
Intended Audience:

This presentation will examine the Heisenberg antiferromagnetic spin chain in one dimension (1D) with a crystal field splitting term and applied magnetic field term. We use theoretical techniques from quantum field theory and conformal field theory (CFT) to make predictions about the excitation spectrum for our model. We then use Density Matrix Renormalization Group (DMRG)  umerical techniques to simulate our spin chain and extract the energy spectrum as we vary our crystal field splitting and magnetic field terms. This work is motivated by recent experimental work  one on SrNi2Vi2O8 by Bera et al. [1] which is a quasi-1D material with weakly coupled spin chains in the bulk.  We first consider our system where the crystal field splitting term is set to zero. Near the critical field, it undergoes a Bose condensation transition whose excitation spectrum can be mapped to non-interacting fermions in 1D. We then consider large negative crystal field splitting. Near critical field, we show that the transition is in the Ising universality, and use results from CFT to predict the spectrum. Finally, we examine our crystal field splitting tuned to the value obtained in Ref. 1, which is a small, negative value.

[1] A.K. Bera, B. Lake, A.T.M.N. Islam, et al. Phys. Rev. B 91, 144414
(2015)
[2] I. Affleck, Phys. Rev. B 43, 3215 (1991)