Néel to spin-Peierls transition in a quasi-one-dimensional Heisenberg model coupled to bond phonons
The zero and finite temperature spin-Peierls transitions in a quasi-one-dimensional spin- 1/ 2 Heisenberg model coupled to adiabatic bond phonons is investigated using the stochastic series expansion (SSE) quantum Monte Carlo (QMC) method. The quantum phase transition from a gapless Neel state...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2014
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/79925 http://hdl.handle.net/10220/18712 |
| Summary: | The zero and finite temperature spin-Peierls transitions in a quasi-one-dimensional spin- 1/
2 Heisenberg model
coupled to adiabatic bond phonons is investigated using the stochastic series expansion (SSE) quantum Monte
Carlo (QMC) method. The quantum phase transition from a gapless Neel state to a spin-gapped Peierls state
is studied in the parameter space spanned by spatial anisotropy, interchain coupling strength, and spin-lattice
coupling strength. It is found that for any finite interchain coupling, the transition to a dimerized Peierls ground
state only occurs when the spin-lattice coupling exceeds a finite, nonzero critical value. This is in contrast to the
pure 1D model (zero interchain coupling), where adiabatic/classical phonons lead to a dimerized ground state for
any nonzero spin-phonon interaction. The phase diagram in the parameter space shows that for a strong interchain
coupling, the relation between the interchain coupling and the critical value of the spin-phonon interaction is
linear whereas for weak interchain coupling, this behavior is found to have a natural logarithmlike relation.
No region was found to have a long range magnetic order and dimerization occurring simultaneously. Instead,
the Neel state order vanishes simultaneously with the setting in of the spin-Peierls state. For the thermal phase
transition, a continuous heat capacity with a peak at the critical temperature Tc shows a second order phase
transition. The variation of the equilibrium bond length distortion δeq with temperature showed a power law
relation which decayed to zero as the temperature was increased to Tc, indicating a continuous transition from
the dimerized phase to a paramagnetic phase with uniform bond length and zero antiferromagnetic susceptibility. |
|---|