In the present paper, we study the zero-temperature phase diagram of the doped perovskite manganitesat filling x = 0.5 by the real-space Hartree-Fock approximation method. Our purpose is to resolve a controversialissu...In the present paper, we study the zero-temperature phase diagram of the doped perovskite manganitesat filling x = 0.5 by the real-space Hartree-Fock approximation method. Our purpose is to resolve a controversialissue arising recently on the origin of the charge ordered phases in these systems. We find that the antiferromagneticsuperexchange interaction between the localized spins plays the central role in producing the concerned phases. Ourresults confirm some speculations on this issue.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
We propose a new method to obtain the correlation length of gapped XXZ spin 1/2 antiferromagnetic chains. Following the relativistic quantum field theory in space-time dimensions, we use the exact dispersion of massi...We propose a new method to obtain the correlation length of gapped XXZ spin 1/2 antiferromagnetic chains. Following the relativistic quantum field theory in space-time dimensions, we use the exact dispersion of massive spinon to calculate the correlation length for XXZ spin 1/2 chain. We conjecture that the correlation length for other 1D lattice models can be obtained in the same way. Relation between dispersion and the oscillated correlation of gapped incommensurate lattice models is also discussed.展开更多
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
文摘In the present paper, we study the zero-temperature phase diagram of the doped perovskite manganitesat filling x = 0.5 by the real-space Hartree-Fock approximation method. Our purpose is to resolve a controversialissue arising recently on the origin of the charge ordered phases in these systems. We find that the antiferromagneticsuperexchange interaction between the localized spins plays the central role in producing the concerned phases. Ourresults confirm some speculations on this issue.
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.
文摘We propose a new method to obtain the correlation length of gapped XXZ spin 1/2 antiferromagnetic chains. Following the relativistic quantum field theory in space-time dimensions, we use the exact dispersion of massive spinon to calculate the correlation length for XXZ spin 1/2 chain. We conjecture that the correlation length for other 1D lattice models can be obtained in the same way. Relation between dispersion and the oscillated correlation of gapped incommensurate lattice models is also discussed.
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.
