Silvia Bacci

Theory of nuclear spin-lattice relaxation in La2CuO4 at high temperatures

The nuclear-spin\char21{}lattice relaxation in

FRUSTRATED SPIN (J-J') SYSTEMS DO NOT MODEL THE MAGNETIC PROPERTIES OF HIGH-TEMPERATURE SUPERCONDUCTORS

{\mathrm{La}}_{2}

2D One-Band Hubbard Model for the Cuprates

{\mathrm{CuO}}_{4}

Strongly correlated electronic systems with one hole: Dynamical properties.

is reexamined in connection with the recent measurements of the NQR relaxation rate for temperatures up to 900 K [T. Imai, C. P. Slichter, K. Yoshimura, and K. Kosuge, Phys. Rev. Lett. 70, 1002 (1993)]. We use an approach based on the exact diagonalization for the Heisenberg model to calculate the short-wavelength contribution to the relaxation rate in the high-temperature region, T\ensuremath{\gtrsim}J/2. It is shown that the spin diffusion accounts for approximately 10% of the total relaxation rate at 900 K and would beome dominant for TgJ. The calculated 1/

Ground-state properties of the S =1/2 Heisenberg antiferromagnet on a triangular lattice

{\mathit{T}}_{1}

Dynamics of one hole in the t-J model.

is in good agreement with the experiment both in terms of the absolute value and temperature dependence.

Derivation of a one-band Hubbard model for CuO planar materials

We study the t—J model with one hole and the frustrated Heisenberg J—J′ model in a square lattice. Specifically, we compute and compare for both, the doped and frustrated models, the dynamic spin-spin structure factor S(q, ω), and the B1g Raman scattering spectrum R(ω) at zero temperature. The behavior of these quantities differs between the t—J and the J—J′ models. We observe that both the B1g Raman spectrum as well as the structure factor for the t—J model are in qualitative agreement with experimental measurements while the corresponding results for the J—J′ model are not. These results indicate that the magnetic behavior of doped systems cannot be accurately modeled by a purely spin Hamiltonian. These results are of relevance to the claim that the effect of adding holes (doping) on the magnetic properties of the quantum Heisenberg antiferromagnet can be described by introducing second and sometimes third nearest-neighbor couplings, J′ and J″ respectively, in the original (undoped) Hamiltonian.

Static and dynamical correlations in a spin-1/2 frustrated antiferromagnet.

We use a high-statistic quantum Monte Carlo and Maximum Entropy regularization method to compute the dynamical energy correlation function (DECF) of the one-dimensional (1D)

Spin-1/2 frustrated Heisenberg model at finite temperature.

S=1/2