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

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

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) numerical 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 done 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)

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