arXiv subjects

Hae-Young Kee

Publications and source records attributed to Hae-Young Kee.

184 records · Page 11Linked to original sources

arXiv1995

Quantitative Description of $V_2O_3$ by the Hubbard Model in Infinite Dimensions

We show that the analytic single-particle density of states and the optical conductivity for the half-filled Hubbard model on the Bethe lattice in infinite dimensions describe quantitatively the behavior of the gap and the kinetic energy ratio of the correlated insulator $V_2O_3$. The form of the optical conductivity shows $ω^{3/2}$ rising and is quite similar to the experimental data, and the density of states shows $ω^{1/2}$ behavior near the band edges.

cond-mat↗

arXiv1995

Analytic Treatment of Mott-Hubbard Transition in the Half-Filled Hubbard Model

The Mott-Hubbard transition in the half-filled Hubbard model is studied analytically for the paramagnetic ground state and the classical Néel state. The single-particle density of states is obtained by calculating the Green's function represented by the infinite continued fraction. The paramagnetic solution shows that the Mott-Hubbard transition is signaled by both collapsing Hubbard bands and appearing $δ$-function peak at midgap, and the transition is second order at the ground state. We also provide specific heats in metallic regime to demonstrate that our results recover those of infinite dimension.

cond-mat↗

arXiv1993

Multi-Channel Kondo Necklace

A multi--channel generalization of Doniach's Kondo necklace model is formulated, and its phase diagram studied in the mean--field approximation. Our intention is to introduce the possible simplest model which displays some of the features expected from the overscreened Kondo lattice. The $N$ conduction electron channels are represented by $N$ sets of pseudospins $\vt_{j}$, $j=1, ... , N$, which are all antiferromagnetically coupled to a periodic array of $|\vs|=1/2$ spins. Exploiting permutation symmetry in the channel index $j$ allows us to write down the self--consistency equation for general $N$. For $N>2$, we find that the critical temperature is rising with increasing Kondo interaction; we interpret this effect by pointing out that the Kondo coupling creates the composite pseudospin objects which undergo an ordering transition. The relevance of our findings to the underlying fermionic multi--channel problem is discussed.

cond-mat↗

arXiv1993

Underscreened Kondo Necklace

It has been suggested recently by Gan, Coleman, and Andrei that studying the underscreened Kondo problem may help to understand the nature of magnetism in heavy fermion systems. Motivated by Doniach's work on the S=1/2 Kondo necklace, we introduce the underscreened Kondo necklace models with S>1/2. The underscreened Kondo necklace is the simplest lattice model on which the competition between Kondo spin compensation, and magnetic ordering due to an RKKY-type interaction can be examined. We used the mean-field approximation to determine the phase diagram, and found that the low-temperature phase is always an x-y antiferromagnet. This contention is further supported by the derivation of the exact form of the effective hamiltonian in the limit of very large Kondo coupling: it is found to be an antiferromagnetic x-y model for the residual (S-1/2)-spins. In general, the degree of moment compensation depends on both the Kondo coupling, and on S.

cond-mat↗