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Dynamic spin susceptibility in thet-J model

G. Dzhakeli, Nikolay M. Plakida

Theoretical and Mathematical PhysicsMar 1, 199810 citations

Dynamic spin susceptibility in the t-J model

George Jackeli, Nikolay M. Plakida

Dynamic spin susceptibility is calculated for the t-J model in the paramagnetic phase by applying the memory function method in terms of the Hubbard operators. A self-consistent system of equations for the memory function is obtained within the mode coupling approximation. Both itinerant hole excitations and localized spin fluctuations give contributions to the memory function. Spin dynamics have a diffusive character in the hydrodynamic limit; spin-wave-like excitations are regained in the high-frequency region.Dynamic spin susceptibility is calculated for the t-J model in the paramagnetic phase by applying the memory function method in terms of the Hubbard operators. A self-consistent system of equations for the memory function is obtained within the mode coupling approximation. Both itinerant hole excitations and localized spin fluctuations give contributions to the memory function. Spin dynamics have a diffusive character in the hydrodynamic limit; spin-wave-like excitations are regained in the high-frequency region.

arXiv:cond-mat/9909019Sep 1, 19991 citation

Static spin susceptibility in the t-J model

Artem Vladimirov, Dieter Ihle, Nikolay M. Plakida

Theoretical and Mathematical PhysicsSep 1, 200711 citations

Projection Operator Approaches to Complex Susceptibility

Chikako Uchiyama

We review two kinds of approaches to obtain the complex susceptibility with using the projection operator methods in Schrödinger and Heisenberg picture. In the complex susceptibility, we include the effect of initial correlation between the relevant system and its environment. Using the method in Heisenberg picture, we show a way to obtain the time evolution of a dynamical variable up to higher orders of system-environment interaction. We apply it to a case of low field resonance where a 1/2 spin interacts with a quantum environment. When we assume the spectral function for system-environment interaction to be described by a Lorentzian function, we find a continued fraction form of the memory term, which enables us to evaluate an arbitrary order of system-environment interaction up to infinite orders. We also show that the method in Schrödinger picture can be used to obtain the time evolution of the response function. With the method, we find a systematic way to treat a multiple-spin system under the effects of its environment. We demonstrate the usefulness of the method by applying it to a three-spin system which interacts with a quantum environment in the Ohmic spectral function.We review two kinds of approaches to obtain the complex susceptibility with using the projection operator methods in Schrödinger and Heisenberg picture. In the complex susceptibility, we include the effect of initial correlation between the relevant system and its environment. Using the method in Heisenberg picture, we show a way to obtain the time evolution of a dynamical variable up to higher orders of system-environment interaction. We apply it to a case of low field resonance where a 1/2 spin interacts with a quantum environment. When we assume the spectral function for system-environment interaction to be described by a Lorentzian function, we find a continued fraction form of the memory term, which enables us to evaluate an arbitrary order of system-environment interaction up to infinite orders. We also show that the method in Schrödinger picture can be used to obtain the time evolution of the response function. With the method, we find a systematic way to treat a multiple-spin system under the effects of its environment. We demonstrate the usefulness of the method by applying it to a three-spin system which interacts with a quantum environment in the Ohmic spectral function.

Progress of Theoretical Physics SupplementJan 1, 20101 citation

Spin dynamics for the t-J model

Zhongbing Huang, Shiping Feng

arXiv:cond-mat/9805308Physics Letters AMay 1, 19985 citations

Charge dynamics and optical conductivity of the t−J model

George Jackeli, Nikolay M. Plakida

The dynamic charge susceptibility and the optical conductivity are calculated in the planar $t\ensuremath{-}J$ model within the memory function method, working directly in terms of Hubbard operators. The density fluctuation spectrum consists of a damped soundlike mode for small wave vectors and a broad high energy peak $(\ensuremath{\sim}t)$ for large momenta. The study of the optical conductivity shows that electron scattering from spin fluctuations leads to the Drude-frequency dependent relaxation rate which exhibits a crossover from ${\ensuremath{\omega}}^{3/2}$ behavior at low frequencies $(\ensuremath{\omega}<2|\ensuremath{\mu}|),$ to a linear $\ensuremath{\omega}$ dependence for frequencies larger than $2|\ensuremath{\mu}|.$ Due to the spin-polaron nature of charge carriers, extra absorptions arise starting at a frequency $\ensuremath{\omega}\ensuremath{\gtrsim}J.$ The obtained results are in a good agreement with exact diagonalization studies.The dynamic charge susceptibility and the optical conductivity are calculated in the planar $t\ensuremath{-}J$ model within the memory function method, working directly in terms of Hubbard operators. The density fluctuation spectrum consists of a damped soundlike mode for small wave vectors and a broad high energy peak $(\ensuremath{\sim}t)$ for large momenta. The study of the optical conductivity shows that electron scattering from spin fluctuations leads to the Drude-frequency dependent relaxation rate which exhibits a crossover from ${\ensuremath{\omega}}^{3/2}$ behavior at low frequencies $(\ensuremath{\omega}<2|\ensuremath{\mu}|),$ to a linear $\ensuremath{\omega}$ dependence for frequencies larger than $2|\ensuremath{\mu}|.$ Due to the spin-polaron nature of charge carriers, extra absorptions arise starting at a frequency $\ensuremath{\omega}\ensuremath{\gtrsim}J.$ The obtained results are in a good agreement with exact diagonalization studies.

arXiv:cond-mat/9810327Physical review. B, Condensed matterAug 15, 199923 citations

Dynamical Spin Susceptibility in the t-J Model: The Memory Function Method

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