Magnetic susceptibility of the two-dimensional Hubbard model using a power series for the hopping constant

[摘要] The magnetic susceptibility of the two-dimensional repulsive Hubbard model with nearest-neighbor hopping is investigated using the diagram technique developed for the case of strong correlations. In this technique, a power series in the hopping constant is used. At half-filling, the calculated zero-frequency susceptibility and the square of the site spin reproduce adequately the results of Monte Carlo simulations. Also, in agreement with numerical simulations, no evidence of ferromagnetic correlations was found in the considered range of electron concentrations 0.8 less than or similar to(n) over bar less than or similar to 1.2 for the repulsion parameters 8 parallel to t parallel to <= U <= 16 parallel to t parallel to. However, for larger U/parallel to t parallel to and parallel to 1-(n) over bar parallel to approximate to 0.2, the nearest-neighbor correlations become ferromagnetic. For (n) over bar less than or similar to 0.94 and (n) over bar greater than or similar to 1.06, the imaginary part of the real-frequency susceptibility becomes incommensurate for small frequencies. The incommensurability parameter grows with departure from half-filling and decreases with increasing frequency. This behavior of the susceptibility can explain the observed low-frequency incommensurate response observed in normal-state lanthanum cuprates.

[发布日期] 2007-12-01

[关键词] INCOMMENSURATE SPIN DYNAMICS;T-J MODEL;TRANSITION METALS;DIAGRAM TECHNIQUE;NEUTRON-SCATTERING;SUPERCONDUCTORS;FERROMAGNETISM;APPROXIMATION;PHASE;TEMPERATURE