We extend a previous result of ours [G.S. Tian, Phys. Rev. B63 (2001) 224413] on the antiferromagnetic spin correlations in the half-filled Hubbard model at finite temperature to the double-exchange model. To overcome...We extend a previous result of ours [G.S. Tian, Phys. Rev. B63 (2001) 224413] on the antiferromagnetic spin correlations in the half-filled Hubbard model at finite temperature to the double-exchange model. To overcome the mathematical difficulty caused by the localized spin freedom in this model, we apply both Zener's argument and the finite-temperature spin-reflection-positivity method to show rigorously that, at any temperature , the spin correlations in the half-filled double-exchange model are predominantly antiferromagnetic. This conclusion is completely consistent with the experimental observations and the previous theoretical results by approximate methods.展开更多
In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction ...In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.展开更多
In the present paper,we study the effect of element substitution for quarter-filled nanoclusters of perovskite manganite by introducing Jahn-Teller type of perturbation interaction to the double-exchange Hamiltonian.U...In the present paper,we study the effect of element substitution for quarter-filled nanoclusters of perovskite manganite by introducing Jahn-Teller type of perturbation interaction to the double-exchange Hamiltonian.Using the unrestricted real-space Hartree-Fock approximation method we find that,the Jahn-Teller electron-phonon interaction plays the central role in producing the phase transition from ferromagnetic phase to CE type antiferromagnetic phase.Not only the Jahn-Teller interaction benefits antiferromagnetic correlation,it also increases the charge density order parameter.These theoretical results provide a guidance to predict the properties and modify the composition of particles of perovskite manganite under nano-scale.展开更多
文摘We extend a previous result of ours [G.S. Tian, Phys. Rev. B63 (2001) 224413] on the antiferromagnetic spin correlations in the half-filled Hubbard model at finite temperature to the double-exchange model. To overcome the mathematical difficulty caused by the localized spin freedom in this model, we apply both Zener's argument and the finite-temperature spin-reflection-positivity method to show rigorously that, at any temperature , the spin correlations in the half-filled double-exchange model are predominantly antiferromagnetic. This conclusion is completely consistent with the experimental observations and the previous theoretical results by approximate methods.
文摘In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50971011 and 10874003)the Beijing Natural Science Foundation (Grant No. 1102025)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091102110038)
文摘In the present paper,we study the effect of element substitution for quarter-filled nanoclusters of perovskite manganite by introducing Jahn-Teller type of perturbation interaction to the double-exchange Hamiltonian.Using the unrestricted real-space Hartree-Fock approximation method we find that,the Jahn-Teller electron-phonon interaction plays the central role in producing the phase transition from ferromagnetic phase to CE type antiferromagnetic phase.Not only the Jahn-Teller interaction benefits antiferromagnetic correlation,it also increases the charge density order parameter.These theoretical results provide a guidance to predict the properties and modify the composition of particles of perovskite manganite under nano-scale.
