SPIN-1/2 HEISENBERG-ANTIFERROMAGNET ON THE KAGOME LATTICE - HIGH-TEMPERATURE EXPANSION AND EXACT-DIAGONALIZATION STUDIES

For the spin-1/2 Heisenberg antiferromagnet on the kagome lattice we calculate the high-temperature series for the specific heat and the structure factor. A comparison of the series with exact-diagonalization studies shows that the specific heat has further structure at lower temperature in addition to a high-temperature peak at T almost-equal-to 2/3. At T = 0.25 the structure factor agrees quite well with results for the ground state of a finite cluster with 36 sites. At this temperature the structure factor is less than two times its T = infinity value and depends only weakly on the wave vector q, indicating the absence of magnetic order and a correlation length of less than one lattice spacing. The uniform susceptibility has a maximum at T almost-equal-to 1/6 and vanishes exponentially for lower temperatures.