An Analysis of Quantum Properties for the Ground State in s=1⁄2 Heisenberg Antiferromagnetic System on a Square Lattice

Abstract

The relationship between quantum fluctuations and Néel-type ordering for the ground state in s=1⁄2 Heisenberg antiferromagnet on a square lattice is discussed in connection with the role of the off-diagonal part of the exchange interaction (flip-flop terms). In particular, the smallest number of flip-flops f(\ ildef) necessary to change the Néel state (the alternative Néel state) into each α−β base are introduced. The probability distribution of α−β bases to (f, \ ildef) for the ground state is obtained in the numerical calculation. The behavior of the staggered magnetisation and the averaged RVB length as to (f, \ ildef) is also investigated.