Quantized lattice dynamic effects on the spin-Peierls transition

Journal article

The density-matrix renormalization-group method is used to investigate the spin-Peierls transition for Heisenberg spins coupled to quantized phonons. We use a phonon spectrum that interpolates between a gapped, dispersionless (Einstein) limit to a gapless, dispersive (Debye) limit. A variety of theoretical probes are used to determine the quantum phase transition, including energy gap crossing, a finite-size scaling analysis, bond-order autocorrelation functions, and bipartite quantum entanglement. All these probes indicate that in the antiadiabatic phonon limit a quantum phase transition of the Berezinskii-Kosterlitz-Thouless type is observed at a nonzero spin-phonon coupling, gc. An extrapolation from the Einstein limit to the Debye limit is accompanied by an increase in gc for a fixed optical (q=π) phonon gap. We therefore conclude that the dimerized ground state is more unstable with respect to Debye phonons with the introduction of phonon-dispersion renormalizing the effective spin-lattice coupling for the Peierls-active mode. We also show that the staggered spin-spin and phonon displacement order parameters are unreliable means of determining the transition. © 2010 The American Physical Society.

Authors: Pearson, C; Barford, W; Bursill, R

• Publication status: Published
• Journal: Physical Review B
• Volume: 82
• Issue: 14
• Publication date: 2010-10-04
• DOI: 10.1103/PhysRevB.82.144408
• EISSN: 1550-235X
• ISSN: 1098-0121
• Language: English