Bosonic representation of one-dimensional Heisenberg ferrimagnets

Yamamoto, Shoji

doi:10.1103/physrevb.69.064426

Cited by 49 publications

(58 citation statements)

References 87 publications

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“…In the conventional spinwave scheme, the spin deviations in each sublattice diverge in the one-dimensional (1D) antiferromagnets, but the quantum as well as thermal divergence of the number of bosons can be overcome in the Takahashi scheme [17] that will be applied to the present antiferromagnetic F-F-AF chain. The AF-AF-F chain is a ferrimagnet, whose magnetization should be nonzero in the ground state but zero at finite temperature, leading to that we can apply the Yamamoto scheme [21,22], where the Lagrange multiplier was introduced directly in the free energy, to our present ferrimagnetic AF-AF-F chain. The detail derivations of the MSW formalism are collected in Appendix A, where the linear modified spin-wave (LMSW) theory, which is up to the order of O(S 1 ), and the perturbational interacting modified spin-wave (PIMSW) theory, which is up to the order of O(S 0 ), are included.…”

Section: Modified Spin-wave Theorymentioning

confidence: 99%

Thermodynamics of spin-1∕2antiferromagnet-antiferromagnet-ferromagnet and ferromagnet-ferromagnet-antiferromagnet trimerized quantum Heisenberg chains

Gao

2006

Phys. Rev. B

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The magnetization process, the susceptibility and the specific heat of the spin-1/2 AF-AF-F and F-F-AF trimerized quantum Heisenberg chains have been investigated by means of the transfer matrix renormalization group (TMRG) technique as well as the modified spin-wave (MSW) theory. A magnetization plateau at m = 1/6 for both trimerized chains is observed at low temperature. The susceptibility and the specific heat show various behaviors for different ferromagnetic and antiferromagnetic interactions and in different magnetic fields. The TMRG results of susceptibility and the specific heat can be nicely fitted by a linear superposition of double two-level systems, where two fitting equations are proposed. Three branch excitations, one gapless excitation and two gapful excitations, for both systems are found within the MSW theory. It is observed that the MSW theory captures the main characteristics of the thermodynamic behaviors at low temperatures. The TMRG results are also compared with the possible experimental data.

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Section: Modified Spin-wave Theorymentioning

confidence: 99%

Thermodynamics of spin-1∕2antiferromagnet-antiferromagnet-ferromagnet and ferromagnet-ferromagnet-antiferromagnet trimerized quantum Heisenberg chains

Gao

2006

Phys. Rev. B

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“…The quantum Hall ferrimagnetic states, or spin unbalanced phases, 24,25 are also a direct manifestation of coherent quantum mechanical tunneling and inter-dot electronic correlations. These states can be described in terms of linear combinations of spin excitons localized in left and right dots, which in turn lead to coherent spin oscillations, e.g., spin counterpart of coherent charge oscillations in H + 2 molecules.…”

Section: Introductionmentioning

confidence: 99%

Spin transitions induced by a magnetic field in quantum dot molecules

Abolfath

Hawrylak

2008

Phys. Rev. B

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We present a theoretical study of magnetic field driven spin transitions of electrons in coupled lateral quantum dot molecules. A detailed numerical study of spin phases of artificial molecules composed of two laterally coupled quantum dots with N = 8 electrons is presented as a function of magnetic field, Zeeman energy, and the detuning using real space Hartree-Fock Configuration Interaction (HF-CI) technique. A microscopic picture of quantum Hall ferromagnetic phases corresponding to zero and full spin polarization at filling factors ν = 2 and ν = 1, and ferrimagnetic phases resulting from coupling of the two dots, is presented.

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“…(see Ref. [13]). α † k and β † k are the creation operators of the ferromagnetic and antiferromagnetic spin waves with momentum k, respectively.…”

Section: Modified Spin Wave Theorymentioning

confidence: 99%

Thermodynamic properties of ferrimagnetic spin chains in the presence of a magnetic field

2006

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We have implemented three approaches to describe the thermodynamic properties of ferrimagnetic (S = 5/2, s = 2) spin chains. The application of cumulant expansion has been generalized to the ferrimagnetic chain in the presence of an external magnetic field. Using cumulants, we have obtained the field dependent effective Hamiltonian in terms of the classical variables up to the second order of quantum corrections. Thermodynamic functions, the internal energy, the specific heat and the magnetic susceptibility are obtained from the effective Hamiltonian. We have also examined the modified spin wave theory to derive the same physical properties. Finally, we have studied our model using quantum Monte Carlo simulation to obtain accurate results. The comparison of the above results and also the high temperature series expansion shows that cumulant expansion gives good results for moderate and high temperature regions while the modified spin wave theory is good for low temperatures. Moreover, the convergence regions of the cumulant expansion and the modified spin wave theory overlap each other which propose these two as a set of complement methods to get the thermodynamic properties of spin models.

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Bosonic representation of one-dimensional Heisenberg ferrimagnets

Cited by 49 publications

References 87 publications

Thermodynamics of spin-1∕2antiferromagnet-antiferromagnet-ferromagnet and ferromagnet-ferromagnet-antiferromagnet trimerized quantum Heisenberg chains

Thermodynamics of spin-1∕2antiferromagnet-antiferromagnet-ferromagnet and ferromagnet-ferromagnet-antiferromagnet trimerized quantum Heisenberg chains

Spin transitions induced by a magnetic field in quantum dot molecules

Thermodynamic properties of ferrimagnetic spin chains in the presence of a magnetic field

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