Numerical-Diagonalization Study of Spin Gap Issue of the Kagome Lattice Heisenberg Antiferromagnet

Understand

We study the system size dependence of the singlet-triplet excitation gap in the $S=1/2$ kagome-lattice Heisenberg antiferromagnet by numerical diagonalization.

• We successfully obtain a new result of a cluster of 42 sites.
• The two sequences of gaps of systems with even-number sites and that with odd-number sites are separately analyzed.
• Careful examination clarifies that there is no contradiction when we consider the system to be gapless.