arXiv subjects

Youngho Park

Publications and source records attributed to Youngho Park.

3 recordsLinked to original sources

arXiv1999

Comparison of the $π$ and $Δ$ operator approximations for the two-dimensional t-J model

We compare the spectra of the new $π$ operator of the SO(5) theory and the conventional $Δ$ operator for the two-dimensional t-J model. We also calculate the weight transferred to the two-hole ground state from half-filling by these operators. We find that the spectra of these operators are quite similar and the weight for the $π$ operator is smaller than the weight for the $Δ$ operator. We argue that the two-dimensional t-J model does not have a good approximate SO(5) symmetry claimed in Ref. 1.

cond-mat.str-el↗

arXiv1999

Charge and spin dynamics of the Hubbard chains

We calculate the local correlation functions of charge and spin for the one-chain and two-chain Hubbard model using the density matrix renormalization group method and the recursion technique. Keeping only finite number of states we get good accuracy for the low energy excitations. We study the charge and spin gaps, bandwidths and weights of the spectra for various values of the on-site Coulomb interaction U and the electron filling. In the low energy part, the local correlation functions are different for the charge and spin. The bandwidths are proportional to t for the charge and J for the spin, respectively.

cond-mat.str-el↗

arXiv1998

Phase diagram of the two-chain Hubbard model

We have calculated the charge gap and spin gap for the two-chain Hubbard model as a function of the on-site Coulomb interaction and the interchain hopping amplitude. We used the density matrix renormalization group method and developed a method to calculate separately the gaps numerically for the symmetric and antisymmetric modes with respect to the exchange of the chain indices. We have found very different behaviors for the weak and strong interaction cases. Our calculated phase diagram is compared to the one obtained by Balents and Fisher using the weak coupling renormalization group technique.

cond-mat.str-el↗