Quantum disorder in the two-dimensional pyrochlore Heisenberg antiferromagnet - art. no. 094412

We present the results of an exact diagonalization study of the spin-1/2 He isenberg antiferromagnet on a two-dimensional version of the pyrochlore lat tice, also known as the square lattice with crossings or the checkerboard l attice. Examining the low-energy spectra for systems of up to 24 spins, we find that all clusters studied have nondegenerate ground states with total spin zero, and big energy gaps to states with higher total spin. We also fi nd a large number of nonmagnetic excitations at energies within this spin g ap. Spin-spin and spin-Peierls correlation functions appear to be short ran ged, and we suggest that the ground state is magnetically disordered.