Precise Estimation of the S = 2 Haldane Gap by Numerical Diagonalization

Abstract
The Haldane gap of the S = 2 Heisenberg antiferromagnet in a one-dimensional linear chain is examined by a numerical-diagonalization method. A precise estimate for the magnitude of the gap is successfully obtained by a multistep convergence-acceleration procedure applied to finite-size diagonalization data under the twisted boundary condition.
Funding Information
  • Japan Society for the Promotion of Science (16K05418, 16K05419, 16H01080(JPhysics), 18H04330)