Spin Susceptibility for the t-J Model.

Xianglin Ke, Feng Yuan, Shiping Feng

The influence of the additional second-neighbor hopping ${t}^{\ensuremath{'}}$ on the spin response of the $t\ensuremath{-}J$ model in the underdoped and optimally doped regimes is studied within the fermion-spin theory. Although the additional second-neighbor hopping ${t}^{\ensuremath{'}}$ is systematically accompanied by the reduction of the dynamical spin structure factor and susceptibility, the qualitative behavior of the dynamical spin structure factor and susceptibility of the ${t\ensuremath{-}t}^{\ensuremath{'}}\ensuremath{-}J$ model is the same as in the case of $t\ensuremath{-}J$ model. The integrated dynamical spin structure factor spectrum is almost ${t}^{\ensuremath{'}}$ independent, and the integrated dynamical spin susceptibility still shows the particularly universal behavior as $I(\ensuremath{\omega},T)\ensuremath{\propto}\mathrm{arctan}[{a}_{1}\ensuremath{\omega}{/T+a}_{3}(\ensuremath{\omega}{/T)}^{3}].$

Artem Vladimirov, Dieter Ihle, Nikolay M. Plakida

Thomas Pruschke, Th. Obermeier, J. Keller

Zhu-Pei Shi, Rajiv R. P. Singh

The T = 0 spin stiffness ρ s and the transverse susceptibility χ ⊥ of the square lattice half-filled Hubbard model are calculated as a function of the Hubbard parameter ratio U / t by series expansions around the Ising limit. We find that the calculated spin stiffness, transverse susceptibility, and sublattice magnetization for the Hubbard model smoothly approach the Heisenberg values for large U / t . The results are compared for different U / t with RPA and other numerical studies. The uniform susceptibility data indicate a crossover around U / t ≈ 4 between weak-coupling (spin density wave) behavior at small U and strong-coupling (Heisenberg) behavior at large U .

Wen‐Long You, Yuli Dong

We study the quantum phase transitions in the two-dimensional spin-orbit models in terms of fidelity susceptibility and reduced fidelity susceptibility. An order-to-order phase transition is identified by fidelity susceptibility in the two-dimensional Heisenberg XXZ model with Dzyaloshinsky-Moriya interaction on a square lattice. The finite size scaling of fidelity susceptibility shows a power-law divergence at criticality, which indicates the quantum phase transition is of second order. Two distinct types of quantum phase transitions are witnessed by fidelity susceptibility in Kitaev-Heisenberg model on a hexagonal lattice. We exploit the symmetry of two-dimensional quantum compass model, and obtain a simple analytic expression of reduced fidelity susceptibility. Compared with the derivative of ground-state energy, the fidelity susceptibility is a bit more sensitive to phase transition. The violation of power-law behavior for the scaling of reduced fidelity susceptibility at criticality suggests that the quantum phase transition belongs to a first-order transition. We conclude that fidelity susceptibility and reduced fidelity susceptibility show great advantage to characterize diverse quantum phase transitions in spin-orbit models.

G. Dzhakeli, Nikolay M. Plakida